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WORKS OF ELLEN H. RICHARDS 

PUBLISHED BY 

JOHN WILEY & SONS 
43-45 East Nineteenth Street, New York 



Laboratory Notes on Industrial Water Analysis: A 
Survey Course for Engineers. 
8vo, 52 pages. Cloth, 50c net. 
The Cost of Cleanness. 

l2mo, v + 109 pages. Cloth. $1.00. 

The Cost of Living as Modified by Sanitary Science. 

Third Edition, Revised. 12mo. 164 pages. Cloth. 
$1.00. 
Air, Water, and Food; From a Sanitary Standpoint. 

By Ellen H. Richards and Alpheus G. Woodman, 
Assistant Professor of Food Analysis, Massachusetts 
Institute of Technology. Third Edition, Revised 
and Enlarged. 8vo. 278 pages. Cloth. $2.00. 

The Cost of Food : A Study in Dietaries. 
12mo. 161 pages. Cloth. $1.00. 

The Dietary Computer. 

By Ellen H. Richards, Instructor in Sanitary Chem- 
istry, Massachusetts Institute of Technology, assisted 
by Louise Harding Williams. $1.50 net. Pamphlet 
separately, $1.00 net. 

The Cost of Shelter. 

12mo. vi + 136 pages. Illustrated. Cloth. . $1.00. 

" Cost of Living " Series. 

1. Cost of Living. 2. Cost of Food. 3. Cost of 
Shelter. 4. Cost of Cleanness. 12mo. Cloth. 4 
vols, in a box. $4.00. 



Published by WHITCOMB & BARROWS 
Huntington Chambers 

The Chemistry of Cooking and Cleaning. 

By Ellen H. Richards and S. Maria Elliott. 158 
pages. Cloth. $1.00. 
Food Materials and their Adulterations. 

183 pages. Cloth. $1.00. 

Home Sanitation. 

Revised Edition. Edited by Ellen H. Richards and 

Marion Talbot. 85 pages. Paper. 25c. 
Plain Words about Food. 

The Rumford Leaflets. Illustrated. 176 pages. 

Cloth. $1.00. 
First Lessons on Food Diet. 

52 pages. Cloth. 30c net. 
The Art of Right=Living. 

50 pages. Cloth. 50c net. 

Sanitation in Daily Life. 

82 pages. Cloth. 65c. net. 



AIR, WATER, AND FOOD 



FROM A SANITARY STANDPOINT. 



BY 



ELLEN H. RICHARDS AND ALPHEUS G. WOODMAN. 

Instructor in Sanitary Chemistry. Assistant Processor of Food Analysis, 

Massachusetts Institute of Technology. Massachusetts Institute of Technology. 



"These cannot be taken as sufficient ... in these times whei) 
every word spoken finds at once a ready doubter, if not an opponent. 
They are. however, specimens, and will serve to- make* comparisons 
in time to come." — Angus Smith. 

"The ideal scientific mind, therefore, must always be held in a 
state of balance which the slightest new evidence may change in one 
direction or another. It is in a constant state of skepticism, knowing 
full well that nothing is certain."— Henry A. Rowland. 



THIRD EDITION, REVISED AND ENLARGED. 

FIRST THOUSAND. 



NEW YORK: 
JOHN WTLEY & SONS. 

London : CHAPMAN & HALL, Limited. 

1909. 



V 



X ** 



Copyright, 1900, 1904. 1909, 



BLLBN H. RICHARDS and ALPHEUS G. WOODMAN. 



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LC Control Number 




tmp96 028456 



PREFACE TO THE THIRD EDITION. 



The great increase of attention to the relations of 
physical environment to mental and moral welfare leads 
the authors to hope that this revised and enlarged edition 
will meet with approval by the body of seekers after truth 
along these lines of study and investigation. 

More clearly than any one else they recognize the omis- 
sions and shortcomings of any book dealing with so compre- 
hensive a subject under the limitations of a short school 
course. Therefore a suggestive rather than a complete 
treatment has been adopted, and a certain conservatism 
has governed the discussion of some subjects which to 
treat fully would require too much space as well as a 
previous training impossible to assume. 

The chapters on analytical methods have been con- 
siderably enlarged; the character of the matter added 
tends to make the work more adapted to the needs of 
the chemical and sanitary engineer as well as to the general 
student and householder. In a subject so rapidly advanc- 
ing the printed page can hardly hope to keep fully abreast 
of the times, but all the methods have been reviewed or 
modified, and tentative ones have been retained or dropped 
as experience has indicated their value. 

The bibliography has been revised and brought up to 
date. 



CONTENTS. 



:haptsr page 

I. Three Essentials of Human Existence i 

II. Air: Composition, Impurities, Relation to Human Life 10 

III. The Problem of Ventilation 19 

IV. Methods of Examination -. 27 

V. Water: Source, Properties, Solvent Power, as a Carrier. 57 
VI. The Problem of Safe Water and Interpretation of Analy- 
ses 76 

VII. Methods of Examination 96 

VIII. Food in Relation to Human Life, Definition, Sources, 

Classes, Dietaries 142 

IX. Adulteration and Sophistication of Food Materials 157 

X. Methods of Food Analysis 167 

Appendices, Tables, Reagents 235 

Bibliogp.aphy .- 263 



AIR, WATER, AND FOOD, 



CHAPTER I. 

THREE ESSENTIALS OF HUMAN EXISTENCE. 

Air, water, and food are three essentials for healthful 
human life. Sanitary Chemistry deals with these three com- 
modities in their relation to the needs of daily existence: 
first, as to their normal composition; second, as to natural 
variations from the normal; third, as to artificial variations — 
those produced directly by human agency with benevolent 
intention, or resulting from carelessness or cupidity. A 
large portion of the problems of public health come under 
these heads, and a discussion of them in the broadest sense 
includes a consideration of engineering questions and of 
municipal finances. This, however, is beyond the scope of 
the present work. 

The following pages will deal chiefly with such portions 
of the subject of Sanitary Chemistry as come directly under 
individual control, or which require the education of indi- 
viduals in order to make up the mass of public opinion 
which shall support the city or state in carrying out sanitary 
measures. 

A notable interest in the subject of individual health as 



■2 AIR, WATER, AND FOOD. 

a means of securing the highest individual capacity both for 
work and for pleasure is being aroused as the application of 
the principles governing the evolutionary progress of other 
forms of living matter is seen to extend to mankind. 

Will power may guide human forces in most economi- 
cal ways, and may concentrate energy upon a focal point so 
as to seem to accomplish superhuman feats, but it cannot 
create force out of nothing. There is a law of conservation 
of human energy. The human body, in order to carry on 
all its functions to the best advantage, especially those of the 
highest thought for the longest time, must be placed under 
the best conditions and must be supplied with clean air, safe 
water, and good food, and must be able to appropriate them 
to its use. The day is not far distant when a city will be 
held as responsible for the purity of the air in its school- 
houses, the cleanliness of the water in its reservoirs, and the 
reliability of the food sold in its markets as it now is for the 
condition of its streets and bridges. Nor will the years be 
many before educational institutions will be held as respon- 
sible for the condition of the bodies as of the minds of the 
pupils committed to their care; when a chair of Sanitary 
Science will be considered as important as a chair of Greek 
or Mathematics; when the competency of the food-purveyor 
will have as much weight with intelligent patrons as the 
scholarly reputation of any member of the Faculty. Within 
a still shorter time will catalogues call the attention of the 
interested public to the ventilation of college halls and dor- 
mitories, as well as to the exterior appearance and location. 

These results can be brought about only when the stu- 
dents themselves appreciate the possibilities of increased 
mental production under conditions of decreased friction, 
such as can be found only when the requirements of health 
are perfectly fulfilled. 



THREE ESSENTIALS OF HUMAN EXISTENCE. 3 

Of the three essentials, air may well be considered first, 
although its office is to convert food already taken into heat 
and energy. Its exclusion only for a few minutes causes 
death, and in quantity used it far exceeds the other two. 
Again, so important is the action of air that the quality of 
food is of far less consequence when abundant oxygen is 
present, as in pure air, than when it is present in lessened 
quantity, as in air vitiated by foreign substances. 

Individual habit has much to do with the appreciation 
of good air, and as our knowledge of the value of an abun- 
dance of this substance in securing great efficiency in the 
human being increases, we shall be led to attach more im- 
portance to the sufficiency of the supply. 

In northern climates air is not free to all in the sense of 
costing nothing, for the coming of fresh air into the house 
means an accompaniment of cold which must be counter- 
acted by the consumption of fuel. A mistaken idea of econ- 
omy leads householders, school boards, and college trustees 
to limit the size of the air-ducts as well as of the rooms. It 
is therefore necessary to emphasize the facts which science 
has fully established, in order to secure the survival of the 
fittest of the race under the present pressure of economic 
conditions, which take so little account of the highest wel- 
fare of the human machine. 

Air, water, and soil are the common possessions of man- 
kind. It is impossible for man to use either selfishly without 
injury to his neighbor and without squandering his inheri- 
tance. Primitive man could leave a given spot when the 
soil became offensive, and neighbors were then too few to 
require consideration; but neither man nor beast could with 
impunity foul the stream for his neighbor who had rights 
below him. The soil is permanent; one knows where to look 
for it and its pollution. Air is abundant and is kept in con- 



4 AIR, WATER, AND FOOD. 

stant motion by forces of nature beyond human control, so 
that, save in the neighborhood of an exceptionally offensive 
factory, man does not often foul the free air of heaven; it is. 
only when he confines it within unwonted bounds that it 
becomes a menace. 

Water is the next precious commodity of the three. 
Without it man dies in a few days; without it the soil is bar- 
ren; without it air in motion parches all vegetation and 
carries clouds of dust-particles; without it there is no life. 
As population increases it becomes necessary to collect as 
much of the rainfall as possible, to store it until needed, and 
to use it with discretion. After use it is often loaded with 
impurities and sent to deal death and destruction to those 
who require it later, and yet, in nature's plan, it is the carrier 
of the world, and rightly treated and carefully husbanded 
there is enough for the needs of all. Its presence or absence 
has been the controlling force in determining the habitations 
of men. In its office of carrier it not only brings nourishment 
in solution to the tissues of the human body, but also carries 
away the refuse material. It is a cardinal principle in all 
sanitary reforms to get rid of that which is useless as soon as 
possible. Too little water allows accumulation of waste 
material and a clogging of the bodily drainage system. 

The average quantity needed daily by the human body is 
about three quarts. Of this a greater or less proportion is 
taken in food, so that at times only from a pint to a quart 
need be taken in the form of water as such. 

Next in importance to quantity is the quality, dependent 
somewhat upon the uses to which it is to be put. As a rule, 
the moderately soft waters are the best for any purpose. 
For drinking purposes water must be free from dangers to 
health in the way of poisonous metals, decomposing matters, 
and disease-germs. For domestic use economy requires; 



THREE ESSENTIALS OF HUMAN EXISTENCE. 5 

that it should not decompose too much soap. Manufactur- 
ing interests require that it should not give too much scale 
to boilers; for agriculture there should not be too much 
alkali. 

From the nature of things, no one family or city can have 
sole control of a given body of water. Those on the high- 
lands may have the first use of the water, which then perco- 
lates to a lower level and is used by the people on the slopes 
over and over before it reaches the sea to start again on 
its cycle of vapor, cloud and rain, brook and river. Al- 
though receiving impurities each time, there are many 
beneficent influences at work to overcome the evils resulting 
from this repeated use. That which is dissolved from one 
portion of earth may be deposited on another. As the plant 
is the scavenger of the air, withdrawing the carbon dioxide 
with which it would otherwise become loaded, so the water 
lias also its plant life, purifying it and withdrawing that which 
would otherwise soon render it unfit for any use. 

Pure water is found only in the chemical laboratory; the 
most that can be hoped for is that human beings may secure 
for themselves water which is safe to drink, which will not 
impair the efficiency of the human machine. 

The importance of the third essential for human life, 
food, and the close interdependence of all three, may be 
clearly shown. Of little use is it to provide pure air and 
clean water if the substances eaten are not* capable of com- 
bining with the oxygen of the air or of being dissolved in 
the water or the digestive juices; of less use still is it to par- 
take of substances which act as irritants and poisons on the 
tissues which they should nourish, and thus prevent healthful 
metabolism and respiratory exchange. 

And yet a large majority of those who have acquired 
some notion of the meaning and importance of pure air and 



6 AIR, WATER, AND FOOD. 

are beginning to consider it worth while to strive for clean 
water pay not the least attention to the sanitary qualities of 
food; the palatable and aesthetic aspects only appeal to 
them. 

Steam-power is produced by the combustion of coal or 
oil. Human force is derived by releasing the stored energy 
of the food in the body. The delicately balanced mechansm 
of the human body suffers even more from friction than the 
most sensitive machine, and the greatest loss of potential 
human energy occurs through ignorance, carelessness, and 
reckless disregard of nature's laws in regard to food. 

It is necessary to know, first, what is the normal compo- 
sition of a given food-material. This is found by analyses 
of many typical samples. Second, is the sample under con- 
sideration normal? To answer this requires an analysis of it, 
and a comparison of the results with standards. If it is not 
normal, in what way does it depart from the standard both 
in healthfulness and in quality? Third, if a food-substance 
is normal, what are its valuable ingredients and in what pro- 
portions are they to be used in the daily diet? 

In regard to meat, milk, and fish, the sanitary aspect for 
the chemist resolves itself into two questions: Is the sub- 
stance so changed as to become a possible source of poison- 
ous products? Or has anything in the nature of a preserva- 
tive been added to it? If so, is it of a nature injurious to 
man? 

There is, however, a great range of quality in some of the 
most abundant foodstuffs, such as the cereals, especially in 
the nitrogen content. This is most important to the vege- 
tarian and to institutions where economy must be practised. 
The following variations in the composition of leading cereals 
will illustrate: 



THREE ESSENTIALS OF HUMAN EXISTENCE f 

,, T ■ Nitrogenous Crude Carbo- i?;w;«. a„v, 

Water - Substance, rat. hydrates. Flbre " Ash ' 

Oats, maximum. ..... . 20.80 18.84 10.65 64.63 20.08 8.64 

" minimum 6.21 6.00 2. 11 48.69 4.45 1.34. 

«• American hulled. 12. 11 13.57 7-68 63.37 1.30 2.03 

Corn, maximum 22.20 14.31 8.87 52.08 7.71 3.93 

" minimum. .. 4- 6 § 5-55 i-73 72-75 0.99 o.Sz 

One sample of wheat flour may contain 14 per cent, of nitro- 
genous substance, another may yield only 9. A day's ration, 
500 grams, will give 70 grams of gluten, etc., in the one 
case and only 45 in the other. This difference of 25 grams, 
would be a serious factor in the dietary of an institution 
where little additional proteid is given, and it alone might 
be the cause of dangerous under-nutrition. 

The next step would naturally be to determine how 
definitely these varying percentages mean varyine nutrition.. 
To this end a study of vegetable nitrogenous oroducts in 
their combination or contact with cellulose, starch, and min- 
eral matter is needed. Much work remains to be done 
before these questions can be even approximately answered. 

At the low cost of one cent a pound, common vegetables 
yield only about one-fifth as much nutriment as one cent's- 
worth of flour, yet they contain essential elements and de- 
serve to be carefully studied. 

Dried fruits and nuts are much undervalued as articles of 
food, as are rice and lentils. (See table, page 150.) 

The discussion of food values will be found in Chapter 

Yin. 

Probably the widest field for the sanitary chemist to-day 
is the study of the so-called predigested foods, infant foods, 
" hygienic " preparations, two-minute cereals, and the count- 
less proprietary packages, which, designed to meet the de- 
mand for quick results, prove traps for the unwary. 

Therefore the sanitary aspect of food demands a study 



8 AIR, WATER, AND FOOD. 

of normal food and food value even more than of adulterants 
or of poisonous food, ptomaines and toxines. The cultiva- 
tion of intelligent public opinion is most important, and each 
student should go out from a sanitary laboratory a mission- 
ary to his fellow men. That is, the office of a laboratory 
of sanitary chemistry should be so to diffuse knowledge as 
to make it impossible for educated people to be deluded by 
the representations of unprincipled dealers. Freedom from 
superstition is just as important in this as in the domain of 
astronomy or physics. So long as chemists are employed 
by manufacturing concerns in making adulterated and 
fraudulent foodstuffs, so long must other chemists be em- 
ployed in protecting the people until the public in general 
becomes wiser. A part of the common knowledge of the 
race should be the essentials of healthful living, in order that 
the full measure of human progress may be enjoyed. 

There is needed a greater respect for food and its func- 
tions in the human body, a better knowledge of its effect on 
the daily output of energy, its absolute relations to health 
and life, and the enjoyment of the same. The familiarity 
with these facts which is given by a few hours' work in the 
laboratory will make a lasting impression and will enable the 
student to benefit his whole life, even if he never uses it pro- 
fessionally. It is purely scientific knowledge, just as much 
as that derived from a study of the phases of the moon or the 
formulae of integration. 

The variety of operations in such work, calling for great 
diversity of apparatus and methods, is an educational factor 
not to be overlooked in laboratory training. 

For all detailed discussions and methods the reader *s 
referred to such works as those of Wiley, Allen, Leach, etc., 
but for the student who needs to study, as a part of general 
education, only typical substances, and such methods as can 



THREE ESSENTIALS OF HUMAN EXISTENCE. 9 

be carried out within the limits of laboratory exercises in 
a college curriculum, the following pages are written. Not 
enough is given to frighten or discourage the student, but 
enough, it is hoped, to arouse an interest which will impel 
him at every subsequent opportunity to seek for more and 
wider knowledge. 

Food is too generally regarded as a private, individual 
matter rather than as a branch of social economy; it is, 
however, too fundamental to the welfare of the race to be 
neglected. Society, in order to protect itself, must take 
cognizance of the questions relative to food and nutrition. 

Formerly each race adapted itself to its environment and 
trained its digestion in accordance with the available food 
supply. In America to-day the question is not how to get 
food enough, but how to choose from the bewildering variety 
offered that which shall best promote the health and develop 
the powers of the human being, and, what is of equal im- 
portance, how to avoid over-indulgence, which weakens the 
moral fibre and lessens mental and physical efficiency. In 
spite of all preaching, few really believe that plain living 
goes with high thinking. Professor Patten says that the 
ideal of health is to obtain complete nutrition. Over-nutri- 
tion as well as under-nutrition weakens the body and sub- 
jects it to evils that make it incapable of survival. 

Xo other form of social service will give so full a return 
for effort expended as the help given toward better diet 
for children and students. Fortunately help is coming fast. 
The United States Government is giving much study to 
food problems, and by publications is making available the 
work of other countries. The later bulletins listed in the 
bibliography at the end of this volume are especially valu- 
able. What is now needed is a general recognition of the 
importance of the subject. 



CHAPTER II. 

air: composition; impurities; relation to human- 
life. 

The average adult human being makes about eighteen 
involuntary respirations per minute. The tidal volume of 
air is from 300 to 500 cubic centimeters (30 cu. in.), about 
2800 cubic centimeters (170 cu. in.) remaining in the lungs 
unless voluntarily expelled by deep breathing. The total 
volume expelled is often called the vital capacity, and is about 
3400 cubic centimeters for men and 2500 for women. Even 
when at rest a volume of 7000 to 12,000 liters (250 to 420 
cu. ft.) of air passes through the lungs of each individual in 
twenty-four hours. Under conditions of exercise more or 
less prolonged or violent this volume may be doubled. The 
composition of the normal inspired air by volume is approxi- 
mately: nitrogen and argon 79 per cent., oxygen 20.9 per 
cent., other constituents 0.1 per cent. The air as it leaves 
the lungs contains nitrogen 79.5 per cent., oxygen 16.0 per 
cent., carbon dioxide 4.4 per cent., and is saturated with 
water-vapor. There has therefore taken place an inter- 
change of gases (called the respiratory exchange), by which 
oxygen has passed into the fluids of the body, and carbon 
dioxide into the air contained within the lung-cells. Only 
about one-fifth of the total oxygen is abstracted during each 
tide. 

If the composition of the inspired air varies from the 



air: relation to human life. ii 

normal, this exchange is disturbed, owing to the difference 
in gaseous pressure and in rate of absorption which this 
variation causes. So delicate is the balance of the active 
forces that serious disturbance of the functions of the living 
organism occurs if the percentage of oxygen is lessened by 
one or two tenths, or if the pressure is raised or lowered by 
a fraction of an atmosphere. It is true that, like a tree 
bending before the wind, the organism soon adapts itself to 
changed circumstances, provided the change is not too great 
nor too suddenly made; but, like the exposed tree, the living 
being is never quite so vigorous and symmetrical as it would 
have been without the effort to overcome disadvantageous 
conditions. 

That a permanent or habitual lowering of the oxygen in 
inspired air must be harmful will be readily seen from a con- 
sideration of the office of this gas in the body. To Lavoisier 
and Laplace we owe the knowledge that animal heat is de- 
rived from a process of combustion. Lavoisier held, how- 
ever, that the seat of this combustion was in the lungs, and 
it is to Pfliiger and his pupils that we are indebted for the 
proofs that it is in the tissues themselves, while the lungs 
serve as a clearing-house or centre qf exchange. 

By the union of the oxygen with the substances found in 
the tissues and brought to them by the circulating fluids of 
the body from the digested food, the heat necessary for the 
life and work of the body is produced. This heat is needed 
to keep the tissues at the temperature at which they can best 
accomplish their work, to give mechanical power for the in- 
voluntary action of heart and lungs, for the processes of 
assimilation, and to furnish the energy for all voluntary work 
and thought. Thus both water and food are intimately con- 
cerned in the processes in which air is an essential factor. 
The statement made in the first sentence of Chapter I is 



12 AIR, WATER, AND FOOD. 

therefore justified, namely, that air, water, and food together 
are three essentials of human existence. A certain relation 
between the three means health, and any disturbance of this 
relation means unhealth, by which term may be designated 
a condition of less than perfect health not yet so serious as 
to be called sickness. 

Air being a mere mixture of the gases nitrogen and oxy- 
gen, in no definite atomic proportions, and carrying varying 
amounts of other substances, gaseous and suspended parti- 
cles, no definite composition can be given. The difference 
between the air over sea or forest plateau and that of city 
streets or of crowded tenements seems only slight if expressed 
in per cent. From 20.98 per cent, of oxygen in the first to 
20.87 an d 20.60 in the last; from .022 per cent, of carbon 
dioxide in the purest air to .045 in cities and .33 in rooms, are 
the common variations; and yet the effect of these apparently 
small differences on human beings subjected to them is very 
noticeable. It is customary to enhance these differences by 
expressing the results in parts per 10,000. 

That the carbon dioxide is of itself a disturbing factor is 
indicated by the observed fact that air which has had the per 
cent, of oxygen reduced by combustion to a point at which 
a candle will no longer burn may be made again a supporter 
of combustion by the removal of the cafbon dioxide. 

A practical application of this principle is made in the 
devices used in diving and in entering mines filled with irre- 
spirable gases. 

There is a sensible effort in breathing, and a feeling of 
discomfort is usually experienced, if the carbon dioxide ac- 
cumulates to ten times the normal amount, or 40 parts per 
10,000 instead of 4. This is probably due to its solubility 
and to its interference with the respiratory exchange, since 
the interchange of gases is influenced by their " partial pres- 



air: relation to human life. 13 

sures." Each gas forming part of a mechanical mixture 

exerts a partial pressure proportional to its percentage of the 

mixture. For example, if atmospheric air, containing 20.81 

per cent, of oxygen, is at 760 millimeters barometric pres- 

20.81 
sure, the partial pressure of the oxygen would be X 

760=158.15 millimeters. The following partial pressures 
of oxygen and carbon dioxide in inspired air and in the lung- 
cells show the extent of variation in different parts of the 
respiratory tract: 

Inspired Air. Lung-cells. 

Oxygen 158.15 mm. 122 mm. 

Carbon dioxide 0.30 mm. 38 mm. 

Gas will always tend to diffuse from the region of high- 
est to that of lowest pressure. Hence the reason for the 
great influence of pressure in causing the diffusion of oxygen 
from the inspired air into the lung-cells and for the converse 
movement of carbon dioxide. That variation in pressure 
has much to do with the discomfort is shown in the so-called 
mountain-sickness, experienced at high altitudes in rarefied 
air, and in the so-called caisson-disease, developed in men 
working in compressed air. If the passage from the caissons 
to the open air is made gradually, there is little trouble, but 
a quick change is often dangerous. A sort of mountain- 
sickness is experienced by many on entering a close room 
from the outside air. Usually this passes away in a measure 
as the organism accommodates itself to the new conditions. 
Even if the symptoms are not severe, there is a dulness or 
an irritability which is not conducive to the best apprehen- 
sion of a difficult subject or to the fullest enjoyment of an 
entertainment. 

This lessening of mental capacity is especially to be de- 



14 AIR, WATER, AND FOOD. 

plore'd in the case of school-children, who are at an age when 
respiration is most frequent and the need of pure air the 
greatest, and also when economy of effort is most demanded. 

It has been said that from the study of the physiological 
effects of close air it seems to be indicated that the evil is 
due to the change in the respiratory quotient and to the con- 
sequent change in blood-pressure, which interferes with the 
circulation. The respiratory quotient is obtained by divid- 
ing the volume of carbon dioxide given off by that of the 
oxygen absorbed, and indicates how much of the oxygen has 
combined with carbon to form carbon dioxide, since one vol- 
ume of oxygen combines with caroon to form one volume of 
carbon dioxide. The rate of exchange is influenced by 
questions of pressure, exposure, temperature, and water- 
vapor or moisture, muscular activity, and the like. 

Water-vapor is the most variable constituent, due to the 
changing capacity of air for moisture at different tempera- 
tures and to the character of the earth's surface. Whether 
over land or water, cultivated or forest region, air at o° C. 
contains only 4.87 grams of water per cubic meter, while air at 
6o° F. (15 C.) can take up 12.76 grams, and at 90 F. holds 
33.92 grams. Since the human body is constancy giving off 
moisture from skin and lungs, and since this exhalation is an 
important factor in the bodily economy, the presence of ex- 
cessive moisture in the air exercises a decided effect. 

On clear, invigorating days the moisture in the air may 
be only 30 or 50 per cent, of that required for complete satu- 
ration at the given temperature, and although the ther- 
mometer reading may indicate 85 ° F. on a hot day, little 
discomfort follows; but let the humidity rise to 90 or 95 per 
cent, while the' temperature remains the same, and oppres- 
sion, restlessness, or languor results. Much the same effects 
are seen in the case of close rooms and crowded halls. The 



air: relation to human life. 15 

watery vapor given off (about 20 grams per person per hour) 
soon saturates the air, and the consequent drowsiness and 
headache usually attributed to carbon dioxide will be felt; 
while if this moisture is removed, the same proportion of 
carbon dioxide would hardly inconvenience the occupants. 
A relative humidity of 60 per cent, is said to be the most 
comfortable for house temperature. 

In normal man, exposure to cold increases the respiratory 
exchange; but if he represses shivering and keeps still by 
force of will, it apparently does not. Politely sitting still in- 
creases the probability of taking cold. A high temperature 
lessens the production of carbon dioxide and therefore saves 
food. This may in part account for the oppressiveness felt 
by well-fed and warmly clothed persons in public places none 
too warm for those with a more restricted diet. 

Muscular activity increases respiratory exchange and 
causes a demand for food. A class of students passing across 
the campus, up several flights of stairs, into a lecture-room 
vitiate the air for the first ten minutes at a rate higher by 
one part of carbon dioxide per 10,000 than half an hour later. 
The exchange is also stimulated by a meal. Not only the 
oxidation of the food itself, but the muscular activity of the 
alimentary canal and probably other accompanying activities 
call for an expenditure of energy which is supplied by in- 
creased heat production. 

Sodium sulphate is said to increase the various respira- 
tory activities, and some have held this, fact to be one reason 
for the beneficial effects of certain mineral waters. 

The amount of carbon dioxide expired is estimated by 
Pettenkofer .at .006 to .012 cubic foot per pound of body 
weight, according to the degree of exertion. Rubner con- 
siders that, in general, metabolic processes depend also upon 
the proportion of superficial area to the total volume of the 



1 6 AIR, WATER, AND FOOD. 

body, hence the smaller the animal the greater the surface to 
the whole mass. Children give off in proportion to their 
body weight about twice as much carbon dioxide as adults. 
Another estimate gives the output of carbon dioxide as 
.0027 gram per hour per square centimeter of surface. 

Ammonia is also a constant component of the air of in- 
habited places and is washed out by rain and snow, as will 
be shown in Chapter VI. 

Of the occasional impurities, probably the most fatal is 
carbon monoxide arising from leaking gas-fixtures or de- 
fective furnaces. This gas has 250 times the affinity for 
haemoglobin and therefore forms with it a more stable 
compound than does oxygen, and hence its presence causes 
a deficiency of the latter gas in the blood, giving symp- 
toms like those observed in mountain-climbing or bal- 
loon ascensions. When the blood-corpuscles become about 
one-third saturated the effect becomes sensible; but if the 
quantity of gas is considerable, the symptoms are hardly 
noticeable before insensibility occurs. For this reason, glow- 
ing charcoal and open gas-jets are the favorite forms of 
cowardly self-destruction. 

In the neighborhood of factories, smelting-works, ore- 
heaps, and of cities burning soft coal there is a noticeable 
amount of sulphurous and sulphuric acids, sometimes so con- 
siderable as to destroy vegetation. 

In places where gas is burned, oxides of nitrogen are 
formed in small quantity, the effect of which is known to be 
harmful. Minute quantities of hydrogen sulphide and of com- 
pounds of carbon and hydrogen and of other gases may be 
present, especially in houses with defective plumbing or in the 
neighborhood of barns, cesspools, and filthy back yards. 
These may reach dangerous proportions, but, like carbon 



air: relation to human life. 17 

monoxide, should not be permitted in or near any well-regu- 
lated household. 

Soot, being insoluble, accumulates in the lungs, as a post- 
mortem examination of persons who have lived for some time 
in a smoky city proves; nevertheless no definite ill effects 
have been as yet attributed to this cause. This again con- 
firms the inference that it is the gaseous constituents, and the 
varying temperature and pressure, which seriously affect the 
respiratory exchange 

The following results, obtained on the air of a large man- 
ufacturing city, will be of interest in this connection: * 

GRAMS PER 1,000,000 CUBIC METERS OF AIR.f 
Soot. H 2 S0 4 . FreeNH 3 . Alb. NH 3 . HNO,. HN0 2 . 

1000 to 40000 7000 to 63000 1 100 to 1000 97 to 557 45 to 1063 o to 155 

1 Partly H a SO s . 

It is probable that much of the danger ascribed to sewer- 
air arises from other causes. Since the atmosphere in sewer- 
pipes is always moist, the only probable source of organisms 
is the splashing of the water. Only about one-half as many 
organisms have been found in the air a'bove flowing sewage 
as in out-door air. Professor Carnelley and Dr. Haldane 
found only one-half as much carbon dioxide and one-third 
as much organic matter in such air as in that of the streets 
above. 

Beyond individual control, and in a measure beyond gen- 
eral control, there exists suspended matter in the air: fine 
volcanic dust, pollen, spores of moulds and algae, dried bac- 
teria, diatoms, small seeds of plants, soot and the finely 
pulverized earth from roads and cultivated and barren lands. 
To this portion of the air we owe beautiful sunsets and dis- 
agreeable fogs. To it manv affections of the throat and 

* Mabery: /. Am. Chem. Soc, 17 (i8qs). 105. 

f See also Bailey: " The Air of Large Towns," Science, Oct. 13, 1893. 
Irwin: "The Soot Deposited on Manchester Snow,"y. Soc. Chem. bid* 
(1902), 533. 



18 AIR, WATER, AND FOOD. 

eyes are due, and by it disease may be transmitted. Some 
kinds of dust lodge in the air-cells and by irritation render 
tke individual liable to disease, as statistics of the mortality 
in dust-producing trades show. In the air of houses this 
impurity increases a thousand-fold by means of the wear of 
furnishings and the accumulation on them of deposited par- 
ticies, by means of furnace-ashes and dried debris of all 
kinds. Only recently have the dangers of this part of the 
air we breathe been distinctly pointed out. 

Aitken * estimated that a cubic inch of air may carry 
2000 dust-particles in the open country, 3,000,000 and more 
in cities, and 30,000,000 in inhabited rooms. Among these 
millions there may be found from ten to several hundred 
micro-organisms, moulds, and bacteria, and, under certain 
conditions, pathogenic germs. 

As methods of culture become more satisfactory and tests 
more universal, it may be demonstrated that many old or 
long-inhabited buildings furnish several varieties of patho- 
genic germs constantly to the air. 

According to some authorities, the most dangerous con- 
tamination of the air is the " crowd-poison," or organic 
matter given off with the carbon dioxide and moisture in the 
breath. References will be found in the bibliography to dis- 
cussions of the subject. No evidence has ever been found 
in the course of investigations in this laboratory, covering a 
period of twenty-five years, that the healthy human lung gives off 
any toxic substance. The same conclusion is reached by Dr. 
Emanuel Formanek of the Hygienic Institute at Prague after 
a long series of critical experiments.f 

* Nature, 31 (187 o), 265; 41 {1886) t 394. 
f Archlv fur Hygiene, 38 (igoo), 1. 



CHAPTER III. 

THE PROBLEM OF VENTILATION. 

From the preceding chapter it will be seen how impor- 
tant is the purity of the air to human well-being, and how 
essential is the diffusion of the knowledge of the methods 
by which it can be secured. It is often said that artificial 
ventilation is a modern necessity. Remains of aqueducts 
and sewers have testified to the sanitary intelligence of his- 
toric peoples, but the ventilating fan does not seem to have 
been included, although natural ventilation by shafts and flues 
has been practised since man came out of cave-dwellings. It 
is true that customs have changed as to many items of daily 
life. In cities more people live on an acre of ground, thus 
fouling the air above and the ground beneath ; more factories 
are belching smoke; more coal is burned; houses are built 
with smaller rooms and less pervious walls; schools and 
lecture-halls are more crowded; people are better fed, con- 
sequently there is more garbage; streets are macadamized, 
allowing finely ground particles to fill the air with every puff 
of. wind; gas-pipes traverse the walls of every house and 
pass under every street; carpets, draperies, and much passing 
in and out cause an accumulation of dust unknown fifty 
years ago. Kerosene lamps require more oxygen than manv 
candles. Besides, people -are becoming less hardy and more 
sensitive physically, so that well-ventilated living-spaces are 
a modern necessity if human efficiency is to be maintained. 

19 



20 AIR, WATER, AND FOOD. 

As we have seen, the air of open spaces presents only 
very slight variation at the same level or for several thousand 
feet above it. The movement of the air caused by the wind 
is usually so rapid, and the reservoir of air for many miles 
above the earth is so immense in comparison with the thin 
vitiated layer, that there are only to be considered enclosed 
spaces in which human beings remain for a period of time. 

To supply the 7000 to 12,000 liters (250 to 430 cube feet) 
of tidal air per person in maximum purity, there must be 
brought to the person at rest some 1800 cubic feet of air per 
hour. If he were in an air-tight chamber 12 feet square and 
8 feet high, a man would reach the limit of purity in 38 
minutes; but no ordinary room is air-tight, and when the 
difference between inside and outside temperature is consid- 
erable, a rapid exchange is taking place even with doors and 
windows shut. 

To secure the passage of this large volume of air through 
a small space without causing a draft that will be objected to 
by the abnormally sensitive victim of modern luxurious 
habits is the problem of ventilation — one not yet satisfactorily 
solved. 

The sanitary engineer is expected to design the appara- 
tus and to aid the architect in so placing and proportioning 
flues, inlets, and outlets as to accomplish the desired results. 
Unfortunately it is too common, especially in the case of 
school and college buildings, to economize in the first cost 
by dispensing with the services of the expert and to leave to 
the builder and " practical " architect all such details. In 
any case, it often becomes necessary to call in the chemist to 
prove the need of reform, or to show by the composition of 
the air whether or not the ventilating plant is doing its work 
efficiently. 

The sanitary inspector, whose business it is to decide 



air: the problem of VENTILATION. 21 

upon the legal questions connected with tenements and fac- 
tories, must often rely upon chemical examinations of the 
air. The validity of these depends not only upon the per- 
fection and delicacy of apparatus and methods used, but also 
upon the judgment and intelligence with which the samples 
are taken. 

Many errors in the construction of buildings have been 
perpetrated because of an ignorance of the physical proper- 
ties of air and, consequently, a mistaken notion of the be- 
havior of a vitiated atmosphere. The lecturer on popular 
science who some forty years ago enlightened (?) the com- 
munity on the chemistry of daily life was accustomed to use, 
as a striking illustration, a glass jar in which a small lighted 
candle was instantly extinguished on pouring into the jar a 
tumblerful of carbon dioxide which had been collected for 
the purpose. The inference was plain: carbon dioxide was 
heavier than air, therefore it falls to the floor and must be 
allowed to flow out as if it were a stream of water. Further 
confirmation of this inference was found in the frequently 
observed fact that a candle lowered into a well often went 
out just before the water was reached. 

Hence for many years the habits of thoughtful persons 
were formed on a belief in the heaviness of carbon dioxide or 
" bad air," and in its tendency to go to the bottom of the 
room and into any holes it could find. This is only another 
instance of danger in half a truth. When do we find cold 
carbon dioxide generated in living-rooms? And how warm 
must the gas be in order to be lighter than the ordinary air? 
How quickly does diffusion take place? Until within a very 
few years the almost unanimous belief among the so-called 
educated classes was that the bad air could be let out by 
opening a window at the bottom, and, in spite of the lessons 
w 7 hich might have been learned by any observant person in 



22 AIR, WATER, AND FOOD. 

hanging pictures or Christmas greens, the common practice 
in private houses, churches, and schools is to open the win- 
dows at the bottom. 

All ordinary vitiation of the air proceeds from a heated 
source. Human breath and warm air are lighter than cold 
air and rise even with their burden of carbon dioxide. It is 
only when they impinge on a very much colder surface, as on 
the window-pane on a very cold day, that they become suffi- 
ciently chilled to fall without mixing with the neighboring 
air. The freedom with which the gases of the air mix, as 
well as the rapidity of the action, may be illustrated in a 
variety of ways. Open a bottle of any volatile and pungent 
substance, as ammonia or hydrogen sulphide, in one corner 
of a room, and almost instantly it may be perceived in the 
most distant part. 

In natural ventilation we have only to avail ourselves of 
these characteristic properties of gases; and whether we wish 
to get rid of the light gases escaping from furnace, stove, or 
gas-pipe, or of the specifically heavier carbon dioxide, or of 
the most dangerous dust, we must furnish an outlet at the 
place to which the fleeing enemy first arrives, lest it turn and 
rend us for our ignorance. 

It is usually sufficient to furnish this opportunity, the 
current caused by this willing escape drawing in sufficient 
fresh air to take its place except in very crowded rooms, and 
even these might be so ventilated provided the whole roof 
were one large ventilating flue. If, however, the air is to be 
drawn from the bottom of the room, its unwilling current 
must be pulled by a superior force, as by an open fire on the 
hearth, which heats the air above it so that, in rushing into. 
the free air above, it draws after it all things movable within 
reach. Then, indeed, even the top of the room becomes 
quickly cleared and no corner can escape; but if the fire be 



air: the problem of ventilation. 23 

long gone out and the chimney cold, the reverse takes place 
and cold, heavy air sinks to the floor, helping to confine the 
bad air at the top of the room. 

What the cold chimney cannot accomplish the mechani- 
cally driven fan can do, namely, by a slight compression 
force a draught even up a cold chimney. In this case the 
very unwillingness of the air to take the prescribed path 
helps in the result as water forced through a miil-wheel de- 
velops mechanical work. The warmed fresh air forced in 
near the top of the room loses its velocity as it mingles with 
that already present, and finds its way along the line of least 
resistance to the opening provided at the bottom of the 
room, into the flue, but only in case there is no easier way. 

Open doors or windows interfere with the prescribed 
course, and blindness to this fact on the part of the occupants 
of mechanically ventilated buildings has caused unjust com- 
plaints of the system. The necessity of regulating the con- 
sumption of fuel and admission of fresh air in accordance 
with variations of temperature, as well as the great care and 
trouble this involves, renders the " natural " system of ventila- 
tion practicable only in less crowded dwelling-houses where 
intelligence can control the varying factors. For schools, 
lecture-halls, or any enclosed spaces occupied by numbers of 
persons at one time, some form of mechanical ventilation 
offers the only hope of good air in cold climates. What 
form that shall take is for the engineer to decide. The chem- 
ist's part is to devise means of readily determining whether 
the persons in charge of the apparatus are using it to gain 
the results designed by the expert. 

As a test of how nearly practice approaches the theoreti- 
cal value, carbon dioxide is taken as the indicator, since it is 
present in a thousand times larger quantitv than any other 
impurity and since it is easily determined. If the air has 



24 AIR, WATER, AND FOOD. 

only the normal amount of carbon dioxide, it is but rarely 
that it contains enough of anything else to be harmful. The 
presence of hydrogen sulphide or of coal-gas is betrayed by 
the odor. Where the gas-supply is " water-gas," contain- 
ing 30 to 40 per cent, of carbon monoxide, there is greater 
danger; but if legal restrictions are complied with, the pres- 
ence of this can be detected in the same way, viz., by the 
odor. 

Danger may also arise from the presence of so-called 
" sewer-gas," which, however, is not a single gas, but a most 
complex and variable mixture of the more volatile products 
of decomposition. For the detection of " sewer-air " chemi- 
cal tests are of little value, since it contains no constituent 
in sufficient quantity and with sufficient regularity to 
serve as an index of its presence. Ill-smelling gases are 
given off only when sewage is about eighteen hours old, 
hence dirty house-pipes are the chief cause of foul air. The 
delicate sense of smell is of value here. Indeed, an edu- 
cated nose is most essential in all examinations of house- 
air. " Crowd-poison," if it exists, keeps company with the 
increase of the products of respiration, and if the incoming 
air is strained or taken from a place free from dust, the par- 
ticles added to the air which is in the rooms will also be re- 
moved with the carbon dioxide. 

From nearly all points of view, carbon dioxide is an indi- 
cator of the efficiency of ventilation, especially if combined 
with observations of temperature and moisture. It is an in- 
dicator also readily understood and accepted by the public. 

The principles of ventilation may be readily illustrated to 
a class by means of simple apparatus. Such an apparatus, 
using candles and designed to illustrate the section of an 
ordinarv room, is shown in Fig. I. 

In testing the efficiency of ventilation of any room or 



AIR: THE PROBLEM OF VENTILATION. 



25 



building, it is necessary to determine first the direction of the 
air-currents, for there can be no ventilation without currents. 
If the architect who designed the building, or the engineer 
who advised the architect, is responsible, then the chemist 
has only to follow directions in taking the samples; but fre- 
quently the chemist, as well as the sanitary engineer, is called 




Fig. 1. — Apparatus to Illustrate the Principles of Ventilation. 

upon to make tests of rooms and buildings of which no plans 
are available. 

In the examination of such rooms, then, the position of 
flues or conduits, both inlets and outlets, which were intended 
to convey air or which serve without such intention, should 
first be located. Possible avenues of ingress and egress by 
means of loose windows, cracks around doors, etc., are to be 
considered. When there is great difference of temperature 
between outer and inner air, these allow of quite rapid change 
of air. Some means of rendering visible these currents is de- 
sirable, such as smouldering paper, magnesium powder, or 
fumes of ammonium chloride. 



26 AIR, WATER, AND FOOD. 

When the direction and intensity of these air-currents 
have been determined, the places from which the air-samples 
are to be taken may be chosen. It will be evident in what 
part of the room stagnation occurs and where eddies are 
formed, also where the air escapes. 

In a room or building without artificial ventilation the 
air-currents are seen to be ascending until they become 
chilled, when they fall. An empty room will not show so 
decidedly the rise of air-currents as will an occupied one in 
which the vitiated air, being much warmer, rises more rap- 
idly and cools less quickly. In taking the samples all acci- 
dental means of contamination must be avoided and the 
occupants must be quiet, for the moving of persons causes 
disturbance in the air-current. There is room for great in- 
genuity in this part of the examination, as circumstances 
greatly modify the method of procedure. A fair sample, or 
a sufficient number of samples to give a fair average, must 
be taken. 

Having secured and analyzed the samples of air, the de- 
cision as to the efficiency of ventilation must be rendered. 

If the room examined is a study- or recitation-room, the 
stratum of air at the level of the students' heads should not 
contain over 8 or 9 parts per 10,000 of carbon dioxide, should 
not show a temperature of over 70 F., nor a humidity of 
over 35 or 50 per cent., and these conditions should be main- 
tained for hours at a time. 

For lecture-halls and spaces occupied for only one hour 
at a time, with ample time between occupation, it is admis- 
sible to allow 9 to 11 parts. If fan ventilation is used, the 
outlet should give the average degree of contamination. If 
no system is used, the air at the top of the room is first 
vitiated; only at the end of twenty minutes to half an hour 
do the lower layers begin to show it. 



CHAPTER IV. 

ANALYTICAL METHODS. DETERMINATION OP CARBON 

DIOXIDE. 

General Statements. — Since the earliest crude attempts 
at the determination of carbon dioxide all chemical methods 
have been based on its absorption by alkalies or alkaline 
earths. It may be the -diminution in volume of the air 
through absorption of the carbon dioxide that is measured ; 
the carbon dioxide may be separated as barium carbonate 
and weighed ; the reduced alkalinity of the absorbing liquid 
may be determined ; or the carbon dioxide may be set free 
from the absorbing solution and its volume determined 
directly ; all of these methods have been used with more or 
less success. For determining with great exactness the 
amount in out-door or " fresh " air it is customary to aspirate 
large quantities of air, sometimes as much as 600 liters, 
through the absorbing solution. For determining the 
amount in the air of rooms a much smaller sample, collected 
in calibrated vessels, of from one to eight liters, is preferable. 

Where it is necessary to absorb large quantities of the 
gas in a slight volume of solution, potassium or sodium hy- 
droxide is used. For nearly all of the " popular tests " cal- 
cium hvdroxide, lime-water, is used because of its harmless 
nature and the ease with which it can be obtained from the 
corner drug store, or from the quicklime procured from the 
mason's barrel. For volumetric methods barium hydroxide 
is generally preferred, because of the less solubility of the 

27 



28 AIR, WATER, AND FOOD. 

barium carbonate, it being only about two-thirds as soluble 
as the calcium salt. The very avidity with which these 
substances take up carbon dioxide is a hindrance to the 
preparation of standard solutions in an atmosphere already 
rich in it. When once prepared the solution must be pre- 
served with especial care, since contact with the hands or a 
whiff of the breath will reduce its strength and vitiate the 
results. All such solutions are best kept in bottles well pro- 
tected from the air by tubes filled with soda-lime and de- 
livered from a burette, as described on page 36. 

Pettenkofer Method. — The method which for many years 
was generally employed for the estimation of carbon dioxide 
in the air of rooms is some modification of that originally 
devised by Pettenkofer.* 

Principle.— In principle this consists in absorbing the 
carbon dioxide from a known volume of air in barium hy- 
droxide solution and titrating the excess with standard 
sulphuric acid. It is essential for the complete absorption of 
the carbon dioxide that the barium hydroxide be largely in 
excess, so that not more than one-fifth of it is neutralized ; 
furthermore, the absorbing solution must be shaken up with 
the air for a considerable time. 

Collecting the Samples.- — The samples are collected in four- 
or eight-liter bottles, the volume of which is accurately 
known, the bottles having been calibrated by weighing them 
filled with water. These bottles are provided with a rubber 
stopper carrying a glass tube over which a rubber nipple 
is slipped. They are filled with the air to be tested by 
means of a pair of nine-inch blacksmith's bellows, fitted 
with valves so arranged as to draw the air cut of the bottle. 
The bellows is connected with a three-quarter-inch brass 

* Pettenkofer: Annalen, 2, Supp. Band (1862), p. 1. Gill: Analyst, 17 (1892), 
184. 



AIR: ANALYTICAL METHODS. 29 

tube reaching nearly to the bottom of the bottle ; fifteen or 
twenty strokes should be sufficient to replace the air in a 
four-liter bottle. At the time of collecting the samples the 
following observations should be recorded: Room, date, 
time, weather, place in room, number of people present, number 
of gas-jets or lamps burning, condition of the doors, windows, 
and transoms; in short, everything that would tend to affect 
the amount of carbon dioxide in the air,, or to cause currents or 
eddies. The bottles should be distinctly labelled and their 
volumes recorded. If the temperature at the point where 
the samples are collected should be essentially different from 
that of the laboratory, the bottles should be allowed to 
stand in the laboratory for half an hour, or until they have 
attained its temperature. 

Directions for Laboratory Work. — The solutions of barium 
hydroxide and sulphuric acid which are used are approxi- 
mately of equal strength; but since it is impracticable to 
prepare exact solutions of barium hydroxide and to keep 
them without change, the exact value of the barium hy- 
droxide solution must be found by titration against the 
standard sulphuric acid, which is made of such a strength 
that 1 cubic centimeter is equivalent to exactly 1 milligram 
of C0 2 . This standardization, as well as the subsequent 
titration, is best made in a small flask to lessen the error 
from absorption of carbon dioxide from the air. It will be 
found most generally satisfactory to measure into the flask 
about 25 c.c. of the barium hydroxide, add. a drop of phen- 
olphthalein solution, and titrate with the sulphuric acid to 
the disappearance of the pink color. In all cases the first 
end-point should be taken as the correct one, because the 
pink color will sometimes return on standing. This is due 
to the presence of minute quantities of potassium or sodium 
hyd^.'^ide in the solution. The alkali sulphates will react 



30 AIR, WATER, AND FOOD. 

with any barium carbonate which may be suspended in the 
liquid with the formation of alkali carbonates which give a 
pink color with phenolphthalein.* The standardization 
should be repeated until consecutive results are obtained 
which check within 0.2 per cent, of each other. 

Determination. — Remove the cap from the tube in the 
stopper of the bottle, insert the tube-tip of the burette so 
that it projects into the bottle, and run in rapidly 50 c.c of 
barium hydroxide from the burette. Replace the cap and 
spread the solution completely over the sides of the bottle 
while waiting three minutes for the burette to drain. In 
doing this take care that none of the solution gets into the 
cap. Note carefully the temperature and barometric 
pressure. Place the bottle on its side and roll or shake it 
at frequent intervals for forty-five minutes, taking care that 
the whole surface of the bottle is moistened with the solution 
each time. At the end of this time thoroughly shake the 
bottle to mix the solution, remove the cap, and pour the 
solution into a stoppered bottle of hard glass of 40 c.c. 
capacity, taking care that the solution shall come in contact 
with the air as little as possible. Under these conditions a 
full well-stoppered bottle may safely stand for days before 
titration. For the titration, measure out with a pipette 
25 c.c. of the clear liquid into a 7 5 -c.c. flask and titrate it 
with the sulphuric acid as in the standardization. The differ- 
ence between the number of cubic centimeters of standard 
acid required to neutralize the total barium hydroxide 
before and after absorption gives the number of milligrams 
of dry carbon dioxide in the sample tested. The results 
may be expressed in parts per 10,000, by volume, under 



* This action can be largely prevented by including a small amount of barium 
chloride when making up the barium hydroxide solution (see p. 247.) 



air: analytical methods. 31 

standard conditions (o° and 760 mm.), saturated with 
moisture (Method 1) or dry (Method 2). Tables for this 
purpose will be found in Appendix A.* 

Example. — Data: Standardization, I c.c. Ba (0H) 2 = 
1.020 c.c. H 2 S0 4 volume of bottle = 8490 c.c; Ba(OH);j 
used = 49.9 c.c. ; H 2 S0 4 used = 21. 1 c.c. ; temperature and 
pressure = 21 and j66 mm. 

Before absorption 

49.9 c.c. Ba(OH) 2 = 49.9 X 1.020 = 50.90 c.c. H 2 S0 4 . 
After absorption 

49.9 c.c. Ba(OH) 2 = 42^2. x 21. 1 = 42.12 c.c. H 2 S0 4 . 

. '. (8490 — 49.9) = 8440. 1 c.c. air contain 50.90— 42. 12 = 

8.78 mg. C0 2 . 

Method 1. — I c.c. C0 2 saturated with moisture at 2 1° and 

766 mm. weighs 1.79624 mg. (Table II, Appendix A). 

8 78 
.-. 8.78 mg. = —7 — =4.887 c.c. C0 2 saturated with 

moisture. 

tt r ■ 1 4.887 

Hence in 10,000 c.c. of air there are -^ — X 10,000 = 

8440. 1 

5.79 parts C0 2 . 

Method 2. — In this method the volume of air is reduced 
to standard conditions of temperature and pressure, under 
which conditions the weight of a cubic centimeter of dry C0 2 
is a constant quantity. 

Thus v' — v{\ + o.oo366(/ / — *°)]. 1/ = 8440.1, f = 21 , 
t° = o° ; hence v = 7837.7 c.c. 

* Dietrich's Table, the one in general use, is not absolutely correct, the 
weight of a cubic centimeter of carbon dioxide at o° C. and 760 mm. being 
somewhat different from that given at present by the best authorities, but 
it is sufficiently close for any but the most exacting work. 



32 AIR, WATER, AND FOOD. 

Also, v : v"=H"\H> or 7837.7 : ^=760: (766— 18.5). 

(18.5 = tension aqueous vapor at 21 .) 

Then v" = 7709 c.c. = volume of air at o° and 760 mm. 

1 c.c. CO2 at o° and 760 mm. weighs 1.9643 mg. 

8.78 4-469 

= 4.469 c.c. CO. — X 10,000 =5.79 parts 



1.9643 " * 7709 

C0 2 per 10,000. 

Two samples are to be taken, closely following the notes, 
and the results calculated by both methods before collecting- 
more samples. Then some one room may be taken and the 
quality of the air determined for the different hours of the 
day, or a comparison of different rooms may be made, or a 
building may be tested as a whole. All data and results ob- 
tained should be arranged in tabular form on a separate page 
of the note-book. 

Notes. — This method of collecting the air in a large bottle 
possesses a decided advantage over the method of slowly 
drawing the air through barium hydroxide contained in a long 
tube, in that a sample represents the condition of the air at 
a given time and not its average condition for a period of an 
hour or so. 

In collecting samples, care must be taken to avoid cur- 
rents of air or the close proximity of people. Duplicate 
samples can be obtained only in empty or nearly empty 
rooms. Even two sides of the same room will probably 
show differences, but two samples taken carefully side by 
side ought to agree within 0.05 part per 10,000. 

While the Pettenkofer method is convenient, and for a 
long time has been the favorite, it is now quite generally 
recognized that it contains inherent sources of error which 
can be obviated only by the use of complicated apparatus 
and extreme skill in manipulation. That the method can 
be employed to obtain results of the highest degree of accu- 



AIR: ANALYTICAL METHODS. 33' 

• racy has been shown by Letts and Blake* in an exhaustive 
study of the question. The refinements found necessary, 
however, place their modification out of consideration for 
ordinary use. 

The principal source of error lies in the necessity for 
titrating the alkaline liquid within the "area of contamina- 
tion," the exhaled breath containing on an average from 
50 to 100 times as much carbon dioxide as the air under 
examination. Other important sources of error which have 
been found to lead to erroneous results are the action of 
the caustic alkali on the glass of the large bottle, and the 
presence of small amounts of the precipitated barium car- 
bonate in the solution during the titration. It should 
therefore be borne in mind that results obtained by this 
method may be too high even though agreeing closely 
among themselves. 

The small bottle to which the solution is transferred for 
settling should be of such a size (40 c.c.) that the volume 
which drains readily from the large bottle when the glass 
tube is flush with the stopper shall a little more than fill it. 
That is, no air-space should be left to serve as a medium for 
transpiration from the surrounding air if the bottle stand 
for some hours. On the other hand, there should be a 
sufficient excess over the 25 c.c needed to ensure the filling 
of the pipette at the first trial. This pipette is globular in 
shape, with a stem of small diameter above and below the 
bulb. The last drop is taken off by touching the neck 
of the flask after counting ten from the time it is 
empty. It is then set upright to drain; the drop which 
collects is gently shaken out before the next titration. 
The error is less than if it were rinsed with water each time. 

All rubber stoppers which are used should first be boiled 

* Proc. Royal Dublin Sec., 9, 107 (iqoo). 



34 AIR, WATER, AND FOOD. 

in dilute caustic soda, then in a dilute solution of potassium 
bichromate and sulphuric acid and thoroughly washed. 

Walker Method. — A comparatively simple method in 
which the errors inherent to the Pettenkofer process are 
avoided has been proposed by Walker.* 

The method has been carefully studied in this laboratory f 
and found to be capable of great accuracy 

Principle. — To a definite volume of air, usually i to 2 
liters, is added a measured amount of standard barium 
hydroxide, care being taken to avoid contact of the solution 
with the air. After the absorption of the carbon dioxide, 
the solution is filtered under reduced pressure through as- 
bestos and the clear barium hydroxide received into a 
known excess of standard hydrochloric acid. The absorp- 
tion vessel is rinsed out with water free from carbon dioxide. 
The excess of acid is then determined by titration with 
barium hydroxide. 

Reagents and Apparatus. — The standard solutions used 
are N/50 hydrochloric acid, and barium hydroxide, approxi- 
mately N/100, its exact strength relative to the acid being 
found daily by titration. It will be found advantageous 
to use solutions of this strength, somewhat more dilute than 
those recommended by Walker, on account of the increased 
accuracy with air nearly free from carbon dioxide. The 
decreased range of usefulness is readily compensated ' by 
the employment of smaller samples of the impure air. 

The barium hydroxide, which is usually made up in 
quantities of 8 liters at a time, is preserved with especial 
care. The hard-glass bottle containing it, placed on a high 
shelf so that the measuring apparatus can be filled directly 
.by gravity, is heavily coated on the inside with barium 

* J. Chem. Soc, jj t IIIO {iqoo). 

■f Woodman : /. Am. Chem. Soc, 25, 150 (iqoj). 



air: analytical methods. 



35 



carbonate. The bottle is closed by a rubber stopper 
with two holes, one of which carries the siphon tube dip- 
ping to the bottom of the bottle and supplying the meas- 
uring burette, while the other carries a fairly large glass T 
(Fig. 2). 



A 



I 



W 




Fig. 2. 



From one-half the horizontal arm of this projects a glass 
tube carrying the device for protecting the solution. This 
device is shown drawn on a somewhat larger scale in the 
same sketch. The horizontal tube enters the T tube far 



36 AIR, WATER, AND FOOD. 

enough to support the apparatus. Connection is made, 
by a closely fitting rubber tube. The longer tube, reaching 
nearly to the bottom of the test-tube, carries a fairly good- 
sized "calcium chloride tube" which contains soda-lime, 
enclosed in the usual manner by pings of cotton. The test- 
tube contains 5 to 10 c.c. cf dilute (about N/50) caustic 
potash colored with phenolphthalein, the whole serving to 
indicate the efficiency of the soda-lime. From the other 
end of the horizontal arm of the T projects in the same way 
a long tube bent at right angles fitting by a rubber stopper 
into the top of the burette, thus making the whole a closed 
system, much after the manner of Blochmann.* Any air 
entering the bottle when the solution is drawn from the 
burette or when the burette is filled again must have come 
through the protecting apparatus. This will be found 
efficient if care is taken in the selection or preparation of 
the soda-lime. t 

The burette used for the barium hydroxide is a glass- 
stoppered one, differing somewhat from the ordinary form. 
The lower portion below the graduations is narrowed and 
bent at right angles. This horizontal part is fitted with an 
ordinary glass stop-cock. This gives no trouble when kept 
well vaselined. The tip of the burette is kept covered with 
a little rubber cap when not in use to prevent clogging from 
the formation of carbonate. The apparatus could easily be 
arranged with a special pipette for the delivery of a definite 
charge of baryta solution if desired. 

The bottles used for the collection of samples are of 
hard glass of about 2 liters capacity, the exact volume being 
determined in each case to a cubic centimeter. The bottle 



* Ann. Chem. (Liebig), 237, 39 (1887). 

f Directions for preparing a good quality of soda-lime are given by Benedict 
and Tower: /. Am. Chem. Soc, 21, 396 (i8qq). 



AIR: ANALYTICAL METHODS. 



37 



is olosed by a rubber stopper through which pass two glass 
tubes about 7 mm. in diameter. The longer tube reaches 
almost to the bottom of the bottle; the shorter tube ends 
internally just flush with the stopper. Both tubes project 
externally about two inches and are provided with stop- 




Fig. 3. 



cocks at slightly different levels so as to permit of convenient 
manipulation. There is permanently attached to the upper 
end of the longer tube a piece of rubber tubing 1 inch in 
length which serves to connect it with the tip of the baryta 
burette. The stop-cocks may be replaced by rubber tubing 
and Mohr pinch-cocks if desired. 



38 AIR, WATER, AND FOOD. 

The apparatus used for filtering off the barium carbonate 
is shown in Fig. 3. 

To the base of a ring-stand is firmly clamped an ordinary 
filter-bottle of about 250 c.c. capacity closed by a rubber 
stopper with two holes. Through one of these passes a tube 
leading to the suction-pump, through the other the tube of 
a Gooch filtering-funnel, the upper part of which is cut off 
so that the remainder above the constriction is about an 
inch long. The tip projecting into the bottle is bent so that 
the liquid shall flow down the side and not spatter. A 
rather close coil of stout platinum wire placed above the 
narrow portion serves as a support for the asbestos filter, 
or can be removed if it is desired to use a cotton plug instead. 
In the upper part of the tube is tightly fitted a rubber 
stopper through which passes a narrow glass tube extending 
to within one-eighth inch of the asbestos layer and provided 
above the stopper with a stop-cock. Connection is made 
with the short tube of the inverted bottle by means of a 
rubber tube about 8 inches in length. 

Procedure. — (a) The Absorption. — Insert the tip of the 
baryta burette into the short piece of rubber tubing and run 
in approximately 50 c.c. with both stop-cocks open. Close 
the outlet cock, pinch the rubber tube with the fingers, 
detach it from the burette and insert a bit of glass rod to 
keep out the air. Finally close the stop-cock. Drain the 
burette three minutes and take the reading as usual. 
Carry out the absorption of the carbon dioxide as described 
in the Pettenkofer method, except that 25-30 minutes is 
ample for the absorption. 

ib) The Filtration. — While the absorption is in progress 
prepare the filter. Apply slight suction and add enough 
asbestos fiber suspended in water to form a felt about a 
sixteenth of an inch thick over the platinum coil. Wash it 



air: analytical methods. 39 

once or twice with distilled water. If properly done the 
water should flow from the filter-tube in a continuous 
stream when the pump is running at good speed, but should 
drop only slowly when the suction is slight. 

Prepare also about ioo c.c. of " wash- water " by adding 
to distilled water i c.c. of a 10 per cent, barium chloride 
solution and three drops of phenolphthalein, then titrating 
with the barium hydroxide to a faint permanent pink. Keep 
in a stoppered flask until wanted. 

Measure into the filter-bottle 25 c.c. of the hydrochloric 
acid. 

The arrangement of the bottle and filter during filtration 
is shown in the figure. 

Open the stop-cock of the shorter tube and turn on the 
pump. Now slowly open the filter stop-cock and control the 
flow of liquid entirely with this cock. The barium carbonate 
remains on the asbestos, and the clear baryta solution which 
passes through is at once neutralized by the hydrochloric 
acid. When all the liquid has passed through allow the 
pump to act for a few minutes to partially exhaust the 
bottle, then close the filter-cock. 

Pour some of the wash-water into a small beaker, dip 
the end of the longer tube into it, .and by opening the stop- 
cock allow about 20 c.c. to flow into the bottle before again 
closing it. Unclamp the bottle and shake thoroughly while 
held horizontally and still attached to the filter. Clamp it 
in place again, turn on the pump, and drain off the wash- 
water. Repeat this twice. Generally at the third washing" 
the wash-water is no longer turned pink, showing that the 
barium hydroxide has been completely removed. Remove 
the stopper and cock from the filter-tube and draw the re- 
mainder of the wash-water through the filter to wash down 
the sides of the tube. 



40 AIR, WATER, AND FOOD. 

(c) The Titration. — Transfer the acid solution tea 6-inch 
porcelain dish and run in barium hydroxide to the produc- 
tion of a distinct pink color. Return the solution to the 
filter-bottle and pour it again into the dish. One or two 
drops of the alkali solution will suffice to finish the titra- 
tion. 

Note. — It will be seen that in this method the errors of 
the other are largely avoided. The alkali solution is made 
weaker, and its time of contact with the glass of the bottle 
is shorter; the barium carbonate is entirely removed if the 
filtration is properly conducted ; the titration is not carried 
out in an alkaline solution, but in one that is acid. 

For a discussion of the results obtained the papers cited 
above may be consulted. 

Strong potassium hydroxide is undoubtedly the best absorb- 
ent for carbon dioxide and in all cases where delicate manipula- 
tion and expensive apparatus are not hindrances, some form 
of gas absorption apparatus is best. The measurement of the 
gas should be made over mercury and in a finely calibrated 
tube. Eimer and Amend now supply a modification of 
the Petterson and Palmquist apparatus which gives good 
results. 

General Tests. — In addition to the above methods for 
determining carbon dioxide just described, there are general 
tests which can often be used with advantage. If within the 
space of a few hours some fifty or more tests are to be made, and 
comparative results rather than great accuracy are required, 
some simpler form of apparatus is desirable. 

Such an apparatus, to be satisfactory, should meet, so 
far as possible, the following requirements: 

(i) It should be sufficiently compact and portable to be 
carried in the hand from place to place. 



air: analytical methods. 41 

(2) It should be as simple in construction as possible, 
and its use should not involve delicate measurements. 

(3) If possible, the apparatus should be made entirely 
of glass, avoiding prolonged contact of corks or of rubber 
connectors with any dilute solution which may be used. 

(4) It should be so constructed as to protect the solution 
at all times from the carbon dioxide of the air, especially 
while the determination is being made, because of necessity 
such an apparatus must be used within the area of contami- 
nation. 

(5) The complete apparatus should be sufficient for fifty 
or more determinations. 

(6) It must be capable of giving results of a reasonable 
degree of accuracy, say within 0.5 part of carbon dioxide in 
10,000 parts of air, in the hands of persons having little or 
no chemical knowledge and minimum skill in manipula- 
tion. 

(7) If a solution be used in the apparatus it should be 
one which can be prepared easily from chemicals readily 
obtained; the solution must maintain its efficiency for a 
reasonable length of time, if protected from external influ- 
ences; and the solution should be one that is not at all 
dangerous or obnoxious to use. 

Simplicity of apparatus is much to be desired, but it 
should not be gained at too great sacrifice of accuracy. Even 
when no greater precision is required than is necessary to 
meet the demands of practical work, it is out of the question 
to measure the test solution by means of an ordinary pipette 
or to preserve it for any length of time in stoppered vials; 
the strength of the solution is almost certain to be reduced 
by contamination with the breath, by contact with rubber 
or cork. 



42 



AIR, WATER, AND FOOD. 



It must ever be borne in mind that extreme care is 
necessary in the preparation and rise of these very dilute 
solutions, the strict observance of conditions which might 
well be neglected in ordinary analytical procedures being 
here an essential factor of success. 

For the preservation and measuring of the test solution 
the authors have devised an apparatus which appears to 
answer the above requirements, and in actual practice has 
been found satisfactory.* 

The essential feature of this apparatus consists of an 
automatic pipette for measuring the test solution. This is 
a modified form of the pipette first pro- 
posed by G. P. Vanier and in use in this 
laboratory for a number of years. A gen- 
eral idea of it may be had from Fig. 4. 
The manner of using it is extremely simple. 
The test solution is preserved in a 1 -liter 
bottle of hard glass provided with a doubly 
perforated rubber stopper. Through one 
opening passes the siphon tube of the pi- 
pette, which is sufficiently long to reach to 
the bottom of the bottle ; through the other 
passes a glass tube ending just below the 
stopper and connected with a small bottle 
containing fresh soda-lime. By means of 
the three-way cock the solution is allowed 
to flow into the small inside pipette until 
it overflows. The stop-cock is then turned 
and the solution allowed to flow out 
at the lowest point. The pipette is 
made of such a size as to deliver exactly 
10 cubic centimeters. The entrance of atmospheric car- 

* Air Testing for Engineers. A. G. Woodman and Ellen H. Richards: Tech. 
Quar., 14, 94 ^9 01 )- 




Fig. 4. — Automatic 
Pipette. 



AIR: ANALYTICAL METHODS. 43 

bon dioxide as the solution flows out is prevented by the 
small tube containing soda-lime or bits of caustic potash, 
The excess of liquid which accumulates in the overflow 
reservoir may be drawn off when desired. The bottle and 
pipette are contained in a wooden case about 20X8x7 inches, 
outside dimensions, and with the solution weigh about 8 
pounds. The case is furnished with a handle at the top so 
that it may be carried readily in the hand from place to 
place. The bottle is fastened to the case, and the lower 
end of the pipette is clamped to a wooden support to keep 
it from swinging. The stopper should be firmly fastened 
to prevent loosening. 

The bottle should be thoroughly cleaned and washed 
with potassium bichromate and sulphuric acid, and it is 
best also to steam it for half an hour or so. As a further 
measure of precaution the rubber stopper is boiled with 
dilute caustic potash and thoroughly washed, although the 
solution can come in contact with it only through splashing 
while the case is being carried. 

This measuring apparatus may be used with a variety of 
methods and with various strengths of solution. 

The general tests are based on two fundamental principles. 
For instance, the Fitz and Wolpert methods are carried out 
by shaking a small quantity of dilute lime-water, colored pink 
by phenolphthalein, with successive portions of air until the 
solution is decolorized. The greater the amount of carbon 
dioxide in the air the less will be the volume of air required 
to neutralize the lime-water, and vice versa. That is, the amount 
of lime-water remaining constant, the amount of carbon 
dioxide will vary in a certain inverse ratio to the volume of 
air. 



44 AIR, WATER, AND FOOD. 

The method of Cohen and Appleyard* is based upon the 
fact that if a dilute solution of lime-water, slightly colored 
with phenolphthalein, is brought in contact with a sample 
of air containing more than enough carbon dioxide to com- 
bine with all the lime present, the solution will be gradually 
decolorized, the length of time required depending upon 
the amount of carbon dioxide present. That is, the quantity 
of lime-water and the volume of air remaining the same in 
each case, the rate of decolorization will vary inversely with 
the amount of carbon dioxide. The method is scientific in 
principle because it recognizes the fact that the absorption 
of carbon dioxide by dilute alkali solutions is a time- 
reaction. 

The method of preparation of the solutions and the 
manner of making the tests which have been found to give 
the best results will be described in detail, since experience 
has shown that these directions cannot be too minute. 

Preparation of the Test Solution. — The solution used is 
a dilute solution of lime-water colored with phenolphthalein. 
To freshly slaked lime add twenty times its weight of water 
in a bottle of such size that it is not more than two-thirds 
full. Shake the mixture continuously for 20 minutes, and 
then allow it to settle over night or until perfectly clear. 
The resulting solution is the stock lime solution, or "satu- 
rated lime-water." If made in the manner indicated, each 
cubic centimeter of it ought to be very nearly equivalent 
to 1 milligram of carbon dioxide. If, however, it is desired 
to know the strength of it more exactly, it may be deter- 
mined by standard acid. 

To prepare the "test solution," pour into the 1 -liter 
bottle of the testing apparatus 1 measured liter of distilled 

* Chem. News, 70, (1894), in. 



air: analytical methods. 45 

water, and add 2.5 ex. of a solution of phenolphthalein (made 
by dissolving 0.7 gram of phenolphthalein in 50 c.c. of 
alcohol and adding an equal volume of water). Stand the 
bottle on a sheet of white paper and add the "saturated 
lime-water " drop by drop from a pipette, shaking the bottle 
thoroughly after each addition until a faint pink color is 
produced which is permanent for one minute. Now add 
6.3 c.c. of the " saturated lime-water," shake, and imme- 
diately connect the bottle again to the apparatus. 

For accuracy in testing air which is high in carbon dioxide, 
it is found advantageous to use a solution twice as strong as 
the above. This double solution is prepared in precisely the 
same way, using 5.0 c.c. of the phenolphthalein solution and 
12.6 c.c. of the " saturated lime-water." 

While this procedure does not give an exact volume of 
solution, it is believed to be the best for the preparation 
of this dilute test solution, since it obviates the necessity 
for pouring the prepared solution from the measuring-flask 
into the bottle in which it is kept; 12.6 c.c. of the stock 
lime solution is added rather than 10 c.c, in order to keep 
the values obtained with the resulting solution more nearly 
comparable with the older values calculated on the suppo- 
sition that 10 c.c. of " saturated lime-water " was equivalent 
to 12.6 milligrams of carbon dioxide. 

Method of Making the Test. — The Fitz shaker or appara- 
tus for measuring the volume of air used, consists of a tube 
of about 30 cubic centimeters capacity, closed at one end, 
and graduated for a distance of 20 cubic centimeters from 
the closed end. In this tube, by means of a rubber collar, 
slides a smaller tube which is contracted at the outer end 
so as to be more readily closed by the finger. The appa- 
ratus is shown full size in Fig 5. 



4 6 



AIR, WATER, AND FOOD. 



See that the inner tube of the shaker slides readily in 
the outer one, moistening the rubber collar slightly if 
necessary. Have the inner tube pressed down to the 

bottom of the larger one, and 
measure into the apparatus 10 
cubic centimeters of the test solu- 
tion from the automatic pipette, or 
from a burette, as in Fig. 2. Pull 
the inner tube up to the 5-c.c. mark 
(the bottom of the inner tube serv- 
ing as the index) and close the end 
of the tube with the finger. Hold 
the apparatus horizontally, and 
shake it vigorously for exactly 30 
seconds. 

The amount of air that is thus 
brought in contact with the solution 
is equivalent to approximately 30 
cubic centimeters, as there are 25 
cubic centimeters of air above the 
liquid when the small tube is forced 
to the bottom of the larger. Re- 
move the finger, press down the 
small tube again to the bottom of 
the larger and draw it up to the 
20-c.c. mark. Shake the apparatus 
again for 30 seconds. The amount 
of air brought in contact with the 
solution is now 30 + 20 = 50 c.c. 
Repeat the shaking, using 20 c.c. 
of fresh air each time, until the 
pink color is discharged. The amount of carbon dioxide 
corresponding to the number of cubic centimeters of air 
used will be found in Table A. 




10 




Fig. 5-— Fitz Shaker. 
Full Size. 



air: analytical methods. 



47 



Acting on the same principle is the Wolpert shaker shown 
in Fig. 50. This cylinder is easier to manipulate and results 
obtained with it by students are more 
consistent than those obtained with the 
Fitz. 

TABLE A. 



Double 




Standard Test 


Solution. 
CO2 in 10,000. 


Cubic Centimeters 
of Air. 


Solution. 
CO2 in 10,000. 


22.2 


5° 


15-6 


18.O 


70 


12.4 


I5- 1 


90 


10.2 


13.O 


no 


8.7 


"•3 


13° 


7-5 


9.9 


15° 


6.6 


8.8 


170 


5-8 


8.0 


190 


5- 2 


7-3 


210 


4.8 


6.8 


230 


4-5 


6-3 


250 


4-3 


5-9 


270 


4.1 


5-6 


290 


3-95 


5-4 


310 


3-8 


5-i 


33° 


H 


4.8 


35° 


3.6 


4-7 


31° 




4-5 


39o 




4.4 


410 




4.2 


45° 




4.0 


490 




3-9 


53o 





I 

The following notes and precautions feiV - 

apply to both forms of the shaker. 
Care should be taken that the finger 
used to close the end of the tube is 
perfectly clean, since on a warm day FlG " 5a ' 

the free acid in the perspiration might easily vitiate the 
results. Some may find the use of a rubber stopper prefer- 
able. 

If greater accuracy is desired, the shaker should be filled 
\rith the air to be tested before running in the test solution. 



48 AIR, WATER, AND FOOD. 

This may be done readily by filling the shaker with water 
and emptying it. 

The apparatus should be shaken vigorously and contin- 
uously during the 30 seconds in order to absorb practically 
all of the carbon dioxide in the enclosed air. The number 
of shakings ought not to be less than 100 during this time. 

Care should be taken not to contaminate the air while 
the sample is being taken. The breath should be held momen- 
tarily while the air in the apparatus is being replaced, and the 
sample should be collected as far to one side of the body as 
possible. It ought not to require over 10 seconds to replace 
the air, and the entire test, with air containing, say, 8 parts 
of carbon dioxide per 10,000, should not require over 6 
minutes. 

If less than 90 c.c. of air is required to discharge the pink 
color, the test should be repeated, using 10 c.c. of air each 
time after the first 30 c.c. 

It is not necessary to rinse out the shaker after making 
each test, but it should be carefully washed and dried after 
using, and the parts kept separate when not in use. 

The " double solution " is used in exactly the same manner 
and amount as the regular test solution, reference being made 
to the appropriate portion of the table. 

For the Cohen method the same solutions may be used 
and measured from the same apparatus. The samples are 
collected in white, glass-stoppered bottles of one-half liter 
capacity. This may be done by aspirating the air with a bel- 
lows, or the bottles may be completely filled with water, which 
is then emptied at the place where the air is to be tested. 

A convenient modification of this is the water siphon method. — 
Two bottles (diameter one-third the height) of nearly equal 
capacity are fitted with rubber stoppers carrying small glass 
tubing, connected by several feet of rubber connector with 



air: analytical methods. 



49, 



clamps (Fig. 6). One bottle is completely filled with water, 
nearly free from carbon dioxide. 

The pair of bottles is taken to the place from which the air 
is to be collected. The inlet tube may be long to reach to near 




Fig. 6. 



the ceiling, or short; if long, the first siphoning should be 
rejected, to secure filling the inlet tube with the air desired, 
the stoppers exchanged, and the sample taken. The air-filled 
bottle is stoppered and taken to the laboratory; or the test 
solution is at once added, the bottle stoppered and shaken, 
noting minutes and seconds. One bottle of water with a small 



.5° 



AIR, WATER, AND FOOD. 



reserve will serve for a number of takings before absorbing a 
deleterious amount of C0 2 . (See Fig. 6.) 

A method involving more preparation but less trouble in 
the field is the steam vacuum method. The steam is supplied 
by a 500 c.c. flask serving as a boiler with a Tirrill burner to 




Fig. 7. — Steam- Vacuum Apparatus. 
From the thesis of Carl E. Hanson, 1908. 



supply the heat. The flask (Fig. 7) is fitted with a rubber 
stopper carrying a No. 6 glass tube bent so that one end extends 
within one half-inch of the bottom of the bottle when placed in 
position on the stand. The bottles used are of about 500 c.c. 
capacity, made for a ground-glass stopper but fitted with a 
rubber stopper. 



air: analytical methods. 51 

To prepare the jet, the water in the flask is allowed to boil 
for five minutes in order to expel completely the air in the 
water and the flask. The pressure should be sufficient to throw 
the vaporized steam at least one foot above the exposed end 
of the tube. 

The empty bottle is placed on the stand in an inverted 
position and allowed to remain for three minutes. In the mean- 
time a thin coating of vaseline is applied half way up the sides 
of the stopper. The vaseline acts as an unguent, reducing 
the coefficient of friction to such an extent that the principal 
resistance is due to the reaction of the stopper against com- 
pression. This enables one to force the stepper in far enough 
t:o bring the glass and rubber into intimate contact, which is 
essential. The vaseline also fills the interstices between the 
rubber and the glass, which makes leakage impossible. 

Protecting the hand with a cloth, the bottle is raised from 
the stand, and the instant it clears the end of the tube the 
stopper is inserted while the bottle is still inverted. The 
stopper may be pushed in more securely by pushing it against 
the table with a few pounds pressure while the bottle is still 
in the inverted position. The stopper is kept in under this 
pressure for a few minutes until the vacuum begins to form, 
after which the atmospheric pressure will keep it in place. 

All the bottles required are treated in the same way. The 
rubber stoppers should be at least one size larger than would 
ordinarily be used for the bottles, and should project three- 
eighths of an inch or more to be easily removed when the sample 
is to be taken. 

Sample bottles may be tested for completeness of vacuum 
by holding them in an inverted position under water at 70 
F., free from carbon dioxide, and removing the stopper. After 
the water has replaced the vacuum, the stopper is inserted and 
the bottle removed. 



5 2 



AIR, WATER, AND FOOD. 



In making the test 10 c.c. of the test solution are run in 
from the automatic pipette, or from a burette as in Fig. 2, 
the time noted, and the bottle shaken continuously and 
vigorously with both hands until the pink color vanishes. 
From the time required the amount of carbon dioxide in the 
air may be found by referring to Table B. 

TABLE B. 



Double Solution. 


Time, 
Minutes and 


"Test Solution.' ' 


Double Solution. 


Time. 
Minutes and 


CO2 in 10,000. 


Seconds. 


CO2 in 10,000. 


CO2 in 10,000. 


Seconds. 


.... 


O.15 


.... 


4.0 


5-45 





O.30 


15-6 




6.00 





o-45 


12. 1 


3-9 


6.15 


16.O 


1. 00 


9.9 




6.30 


i3-i 


i-i5 


8.4 


3*8 


6-45 


11.4 


1.30 


7.2 




7.00 


IO.I 


i-45 


6.3 




7-i5 


9.1 


2.00 


5-5 


3-7 


7-3° 


8-3 


2.15 


4.9 






7.6 


2.30 


4.4 






7.0 


2.45 


4.0 






6-5 


3.00 


3-8 






6.1 


3-i5 


3-7 






5-7 


3-3° 


3-6 






5-4 


3-45 








5-i 


4.00 








4.9 


4-i5 








4-7 


4-3° 








4-5 


4-45 








4-3 


5.00 








4.2 


5-*5 








4.1 


5-30 









Carbon Monoxide. — The detection and estimation of 
carbon monoxide in the very minute quantities in which 
it is found in the air of ordinary rooms is a problem of 
considerable difficulty. 

Detection. — Probably the most convenient test for detect- 
ing small quantities is the blood test. Dilute a large drop 
of human blood, freshly drawn by pricking the finger, to 10 
c.c. with water. Divide the solution into two equal portions, 
and shake one portion gently for ten minutes in a bottle 
containing about 100 c.c. of the air to be tested. Compare 
the tints of the two portions by holding them against a well- 



air: analytical methods. 53 

lighted white surface. The presence of carbon monoxide is 
indicated by the appearance of a pink tint in the blood which 
has been shaken with air. One part in 10,000 can be de- 
tected in this way.* The delicacy of the test can be increased 
by examining- the blood, after shaking with the air, with 
a spectroscope. By collecting the sample in an 8-liter bottle 
and examining it in this way 0.01 part m 10,000 may be detected. 
Determination. f — Principle. — Oxidation of the carbon 
monoxide to carbon dioxide by iodine pentoxide, iodine 
being liberated according to the following equation: 

I 2 5 + 5 CO = I 2 + $co 2 . 

N 

The iodine is titrated with sodium thiosulphate. 

1000 r 

Directions. — Place 25 grams of iodine pentoxide, free from 

iodine, in a small U tube which is suspended in an oil-bath 

and connected with a small absorption-bulb containing 0.5 

gram of potassium iodide dissolved in 5 c.c. of water. Heat 

the oil-bath to 150 C, and pass the air, previously drawn 

through U tubes, — one containing sulphuric acid and the 

other solid potassium hydroxide, — through the apparatus at 

the rate of a liter in two hours. Titrate the liberated iodine 

N 

bv sodium thiosulphate and starch. 

J 1000 l 

Notes. — The temperature and barometric pressure should 
be noted and all volumes reduced to o° C. and 760 mm. pressure. 

Using 1000 c.c. of air, it is possible to determine in this 
way 0.25 part per 10,000, by volume, of carbon monoxide. 

The use of tubes containing sulphuric acid and potassium 
hydroxide is to free the air from unsaturated hydrocarbons, 
hydrogen sulphide, sulphur dioxide, and similar reducing gases. 

* Clowes: " Detection and Estimation of Inflammable Gas and Vapor in 
Ihe Air," p. 138. 

t Kinnicutt and Sanford: Jour. Am. Chem. Soc, 22 (1900), 14 



54 AIR, WATER, AND FOOD. 

Nitrites- — The determination of the amount of nitrites 

or nitrous acid in the air can be readily made as follows: 

Collect a sample of the air in a calibrated eiodit-liter bottle, 

as in the determination of carbon dioxide. Add ioo c.c. of 

N 
approximately — sodium hydroxide solution. (This should 

be free from nitrites and is best made by dissolving metallic 
sodium in redisti led water.) Shake the bottle occasionally 
and let it stand for about twenty-four hours. Take out 50 
c.c. of the solution and determine the amount of nitrites as 
directed on page 108. 

Micro-organisms. — For the quantitative determination 
of the number and distribution of the micro-organisms in air, 
the method employed by Tucker * in the examination of the 
air of the Boston City Hospital answers very well. The 
apparatus used consists essentially of three parts: (1) a 
special glass tube called the aerobioscopc, in which is placed 
the filtering material; (2) a stout copper cylinder of about 
sixteen liters capacity, fitted with a vacuum-gauge; (3) an 
air-pump. The filtering medium which is used to retain the 
micro-organisms is a narrow column of sterilized granulated 
sugar about four inches long. 

In using the apparatus, the required amount of air is first 
drawn from the cylinder by means of the air-pump. A 
sterilized aerobioscopc is then attached to the cylinder and the 
air is slowly drawn through it, leaving its germs in the sugar- 
filter. After the air has been drawn through, the aerobioscopc 
is taken to the culture-room and the sugar dissolved in 
melted sterilized nutrient gelatine. The ge'atine is con- 
gealed in an even film on the inside of the tube, where, after 

* Report State Board of Health, Mass., 1889, 161. 



air: analytical methods. 55. 

'four or five days, the colonies will develop, and can be 
counted by the aid of squares engraved upon the glass. 

This method possesses several peculiar advantages. The 
use of a vacuous cylinder allows a known volume of air to be 
readily aspirated, and the rate of flow through the filter is 
easily controlled. Another great advantage is the use of a 
soluble filter (sterilized granulated sugar), since insoluble 
substances seriously interfere with the counting. Further- 
more, the removal or transference of the filter and its germs 
is avoided. The apparatus is portable, and the method, as 
compared with others, is exceedingly rapid of execution. 

Organic Matter. — In regard to the presence of organic 
matter in the air there is at present considerable variance of 
opinion. While some investigators have obtained results- 
which indicate the presence of such organic matter, it has 
been found also that the amount which is obtained is very 
much less when the dust of the air is first removed by filtra- 
tion. The quantity of organic matter is therefore closely re- 
lated to the amount of dust, and there is strong evidence that 
this dust in the air is the source of the greater part, if not all,, 
of the organic matter, unless there are present persons with 
decayed teeth, diseased lungs, etc. 

The methods of determination that are in general use 
may be divided into two groups. In the first group are 
those methods in which the organic matter is converted into 
ammonia and determined by Nessler's reagent. In the sec- 
ond group the organic matter is oxidized by boiling with 
dilute potassium permanganate, the excess being titrated 
with oxalic acid. No one method gives results which are 
wholly satisfactory, the chief difficulties being to secure an 
absorbing material which shall itself be free from organic 
matter, and to avoid the introduction of minute particles of 
organic matter or dust during the analytical process. 



56 AIR, WATER, AND FOOD. 

Remsen * and Bergey f recommend the use of freshly- 
ignited granular pumice-stone contained in a narrow glass 
absorption-tube. After aspirating a known volume of air, 
the pumice-stone is transferred to a flask, the ammonia dis- 
tilled off from alkaline permanganate and estimated by Ness- 
ler's reagent. Experience with the method in this labora- 
tory has shown that it is practically impossible to prepare the 
pumice-stone so that it shall be absolutely free from organic 
matter, and that the mere act of transference of the absorb- 
ing material resulted in a considerable error. Miss Talbot J 
iound, furthermore, that all of the organic matter is not con- 
verted into ammonia by a single distillation, but that a second 
and third redistillation of the distillates uniformly gave 
higher results. She found it preferable to draw the air 
directly through the boiling permanganate, having the ap- 
paratus so arranged that the condensed steam was returned 
to the flask. In this way the particles of organic matter were 
returned again and again to be acted upon by the perman- 
ganate. 

Experience with all these methods is well summed up by 
Professor Remsen when he says: " It would be useless to 
have examinations of air made by any but the most careful 
workers. It would be time thrown away to have such an- 
alyses made by the average practical chemist.'* 

Dust and Soot — The dust in the air may be estimated by 
drawing a measured volume through tubes packed with cot- 
ton and noting the increase in weight. Soot may be deter- 
mined by drawing the air through combustion-tubing partly 
filled with ignited asbestos, and then determining the carbon 
by the ordinary methods of combustion. 

* National Bd. Health Bulletin, I, 233; II, 517. 

f Mis. Coll. of Smithsonian Institution, No. 1037 (1896). 

X Tech. Quart., 1 (1887), 29. 



CHAPTER V. 

WATER : ITS SOURCE, PROPERTIES, AND RELATION TO LIFE 

AND HEALTH. 

{From the Householder' s Standpoint.) 

The metabolism which produces human energy is depen- 
dent upon the presence of water in the tissues. This water 
is derived in part from food which, as eaten, contains from 
30 to 95 per cent.; in part from boiled water, as in tea and 
coffee; or raw from well or city tap. The total daily supply 
per person for this purpose from all sources is five or six 
pints. 

Water is also necessary to all forms of vegetable and 
animal life, even the lowest types, including those inim'cal 
to human health. Man has always used water as his beast of 
ourden: to carry ships to the ocean, to turn mill-wheels, to 
generate electrical power. He has also forced it to be his 
scavenger, carrying the refuse of his activities out of his sight. 
Unless compelled by legal restrictions, he has given little 
thought to the effect on his neighbor of this treatment of 
their common property. 

In common law, water is held to be a gift of nature to 
man for use by all, and therefore not to be diverted from its 
natural channels for the pleasure or profit of any one to the 
exclusion of the rest. Neither has one the right to return 
to the channel water unfit for the use of his neighbor farther 

down the stream. That is, there is no private ownership in 

57 



5« 



AIR, WATER, AND FOOD. 



surface-waters flowing in natural channels. But this inter- 
pretation of eminent jurists has not always been strictly fol- 
lowed. Many cases have been decided, especially since the 
rapid growth of large cities, in direct contradiction to this 
law. As population increases, cities need to go farther and 
farther into the country for their water-supply, and they 
often take from the few settlers found there the right to the 
water which passes their doors, for the benefit of far-away 
thousands. 

The law in regard to that portion which never enters, or 
which escapes from visible channels, is less clear. It is usu- 
ally held that this water goes with the soil, and that rights 
to it may be bought and sold: that wells may be driven and 
drains dug, even if a neighbor's supply is cut off; but it is 
always maintained that no man has a right to place any sub- 
stances on or in the ground which shall render his neighbor's 
well unfit for use. 

The changes in conditions of life have rendered impera 
tive a careful study of the ways and means of practically com- 
plying with the law's demand without a serious restraint upon 
the progress of civilization. 

The daily quantity required for each person has increased 
from the two ^o four gallons drawn by bucket from the farm- 
house well to thirty or forty gallons taken from the town sup- 
ply by the turning of a faucet, and in cities where much is used 
for manufacturing purposes, for running elevators and 
motors, the daily amount may reach ioo gallons per inhabi- 
tant. This constantly increasing use of water for other than 
cleansing purposes has enormously increased the difficulty 
of securine dean water for domestic use. Not only is a 
larger quantity of polluting material deposited in the water, 
but it is carried farther from its source by the dilution. 
This fact, as well as the demand for higher standards of 



water: source, properties, and relation to life. 59 

purity, has made the abandonment of private water-supplies 
a necessity, and has demanded from municipalities the best 
scientific knowledge and the most careful supervision of the 
quality of the public supply. 

A city or town is under as strict obligation to furnish a 
safe supply of water as it is to provide safe roads. To this 
end, the proper construction and maintenance of reservoirs 
and a sufficient police surveillance of the watershed is as im- 
portant as abundance of supply. 

Education of the people at large is still necessary, not 
only that those who depend in whole or in part upon springs 
and wells may know how to protect themselves, but also that 
the necessary cost of the larger public (municipal) supply 
may be cheerfully paid for by the citizens. 

Leaving out of the present discussion such considerations 
as belong only to the engineer and specialist, the problem of 
potable water will be treated in this chapter from the point 
of view of the intelligent citizen and educated individual who 
cannot afford to remain ignorant of so important a factor in 
the general welfare. The reason why this education is needed 
lies in the fact that primitive habits of thought, influencing 
action in every-day life, survive long after the race has passed 
beyond the original conditions. In no respect is this more 
true than in regard to water. 

The ideal drinking-water of most persons is the dear,, 
colorless, sparkling water of a spring, refreshing in its cool- 
ness and satisfying the aesthetic sense by its suggestion of 
purity. So strong a hold has this ideal that it is most diffi- 
cult to convince the average person that any water which has 
these characteristics can be other than wholesome and, con- 
versely, that w r ater lacking in any of these qualities is suitable 
for human consumption. Early man drank clear cool water 



60 AIR, WATER, AND FOOD. 

wherever he found it. If there was not a spring at hand, he 
scooped out a hole in the sand. Pioneer settlers dug the 
well as near the kitchen door or the barnyard as they could 
find water, with a blind faith in the protecting power of 
mother earth, not wholly misplaced so long as the require- 
ments of the household did not exceed two or three gallons 
per person daily, and so long as the nearest neighbor was 
half a mile away. So persistent is this confidence in nature 
that in the light of this day a majority of intelligent people, 
even, will quaff at a roadside well or drink freely at a country 
hotel or go to live in a city without ever taking thought for 
the quality of the water. Water is water, and he who pauses 
with his glass half-way and asks whence comes the supply is 
scouted as a weak-minded crank. So, too, when town au- 
thorities have spared no pains or expense to secure a safe 
supply from a distant lake, and have guarded it by all means 
known to science, the primitive habit of thought requiring 
colorless water of an even coolness of temperature leads 
those who can afford it to purchase " spring "-water in jugs 
and bottles, with the blind faith of the savage that what comes 
out of the ground must be good. 

Fundamental race-habits are taken advantage of by the 
dealer in spring-waters as well as by the vendor of patent 
medicines — the missionary has no chance against him. 
From the schools and colleges there should, however, 
be sent out a generation of more intelligent persons who, 
learning to weigh evidence, will not take chances and 
will help to develop a public opinion on sanitary matters, 
especially in regard to water-supplies. For not until 
there is an intelligent public can the present reckless use of 
water and ground be stopped. While no^ everv man may 
be a chemist, he can have that modicum of knowledge which 
will enable him to understand the need of chemical tests of 



water: source, properties, and relation to life. 6i 

water and to distinguish between the work of the expert and 
the amateur. 

However safe this ideal of clear, colorless water may have 
been in early times, it must now be relegated, with the un- 
barred door and unwatched treasure, to the mountain fast- 
nesses. As the country becomes settled, appearance and 
taste are no longer sufficient guides; therefore scientific tests 
must be applied and the results interpreted by trained ob- 
servers to whom the individual subordinates his private 
judgment. 

The ideal water should be above suspicion, for if it has 
once been contaminated, who can tell how soon it will find 
bad company again? Not the analyst in his laboratory. In 
fact, the laboratory verdict is worth very little without a 
knowledge of outside conditions and without a keen detec- 
tive insight which scents out the most unlikely causes. 
Nevertheless the evidence given by analytical results is 
needed to procure conviction. 

Although " pure " water is found only in the laboratory, 
" safe " water, that which is reasonably free from objection- 
able substances, mineral and organic, may be obtained with 
sufficient care and knowledge. 

A clear understanding of the problem requires a close 
study of the circulation of water on the earth. Let us trace 
the course of water from sky to ocean, in view of its availa- 
bility for domestic use, and note the dangerous properties it 
may acquire, considering also the changes in condition which 
it may undergo in its course from mountain to sea. 

Water-vapor rising from sea and land is condensed in the 
upper air, then falls to the earth, absorbing, as it does so, 
ammonia, carbon dioxide, sulphur oxides, and other soluble 
gases, if present, and washing the air free from dust-particles, 
mineral and organic. 



62 AIR, WATER, AND FOOD. 

This meteoric water (rain or snow), although nearly free 
from dissolved mineral substances, is therefore by no means 
pure. Furthermore, rain falling on insoluble rocks, bare or 
lichen-covered, or on loose, sandy soils, washes them also, 
giving up to the vegetation the ammonia and taking in re- 
turn carbon dioxide and dissolved albuminoid ammonia. 

Water thus enriched has increased solvent power on cer- 
tain rocks and soils. This rain-water soon forms rivulets 
which, passing down from the highlands into the forest, spread 
over the moss-covered area, soaking the leaves and peaty soil 
and extracting organic substances. Mountain brooks, as well 
as lowland streams, draining a region free from limestone, are 
thus colored brownish-yellow and furnish " meadow-tea/' as 
Thoreau happily named it. As the stream flows on it re- 
ceives contributions of many kinds — the overflow of springs, 
the under-drainage from cultivated fields, the surface-wash 
from pasture and meadow. Scavengers are, however, con- 
stantly at work. Brought as dust by the ever-passing air- 
currents, seeds of tiny plants freely sprout in the water and 
grow rapidly whenever a quiet pool or lake gives oppor- 
tunity. The products of organic decay and the ammonia of 
the rain may be thus removed and the water pass on to the 
reservoir clear and soft and as nearly pure as nature furnishes. 
It is, however, becoming rare to find even a mountain stream 
or forest brook which has not been subjected to modification 
by human agencies. Three kinds of contamination may take 
place. First: A farmhouse high up on the hillside lays trib- 
ute for drinking purposes upon that water finding its way 
beneath the sand which appears in the form of a spring. The 
overflow is made into a duck-pond, or passes through the 
watering-trough by the roadside before it joins other water 
tumbling over the rocks as a rapid stream. The brook thus 
grown larger widens out a little below the farmhouse into a 



water: source, properties, and relation to life. 63 

shallow pool, in which one or two cows frequently seek com- 
fort. The water has become rich in organic matter and sup- 
ports a thick growth of tiny plants; the stones, even, may be 
coated with green slime. This vegetation serves as a warning 
to the hunter and the woodsman, who wisely drink only of 
water from clear pools with bottom of shining sand. The 
heavy material stirred up by the cattle soon settles, leaving 
the water in the stream below clear, although probably a little 
yellow in color. It still tastes well and looks all right, and 
may be used by human beings with probable impunity. 

Second: The little stream next passes other farm build- 
ings, where the privy is put over it to save the trouble of 
cleaning, or, even if not so close, is placed in such a way as to 
allow of a possible wash into it, especially in times of sudden 
rain. 

A case of typhoid fever develops at this farm. No pre- 
caution is taken to disinfect the discharges, and a portion of 
the dangerous material is carried into and along with the 
water. Some two or three miles below, another farmhouse, 
having no spring, uses this same little stream for its supply, 
perhaps damming it up into a little pond or pumping it into 
a tank. All unconscious of what has happened above, or 
ignorant of consequences, this water with a history is freely 
used, and perhaps the whole family come down with the dis- 
ease, perhaps only the delicate one may have it. It may be 
that they will all escape, owing to the fact that they were 
particularly robust, or that they drank no water raw, or that 
the conditions on the stream have been favorable to purifica- 
tion of the water by storage and consequent growth of the 
green plants, which are our friends in such cases; but if the 
water were pumped into a covered tank and used soon after, 
the chances are nine to one that some deleterious results 
followed. 



64 AIR, WATER, AND FOOD. 

Third: A part of the water sinks through the sand, and by 
this filtration becomes freed from all suspended matter and 
consequently from the germs of disease, if present. In its 
course if it is intercepted and collected in a shallow well it 
may again be of great organic purity and free from danger, 
but it will surely bear the telltale marks of its progress in 
the increase of chlorine and solids which will have escaped 
all the agents of purification, and in the nitrates, the result of 
the process. 

It will be noticed that it is only after contamination with 
the " waste of human life " that danger comes to other human 
beings and that many circumstances modify that danger. 
The chances are about equal to those of fire; and as most 
householders think it worth while to insure against possible 
fire, so they should hold the chemist's certificate as a sort of 
water insurance; but since the fire policy does not protect 
from carelessness, the knowledge that the water-supply is 
once good does not absolve the householder or the citizen 
from the greatest care in protecting his premises. Duty to 
his neighbor should lead him to see that this coin of the 
world is passed on in as good condition as possible, and he 
should at least give notice of danger when he knows that it 
exists. 

But this general movement of water on and near the sur- 
face is not all the story. From 25 to 40 per cent, of the 
annual rainfall, in temperate regions, soaks at once into the 
ground, and passing downward through the soil to hard-pan, 
to clayey or impervious layers, or to rock surface, thence 
through crevices, broken joints, or glacial drift-deposits to 
the water-table, flows along the slope for many miles, until 
it finds its way again to the surface, either from the bottom 
of a lake, the bed of a river, the side of a hill, supplying wells 
or appearing as a spring free from all organic and suspended 



water: source, properties, and relation to life. 65 

matter but often rich in gases. In any one of these courses 
it may be intercepted by man and caught or pumped for his 
use. Such water may never have been far from the surface;, 
it may have been used and returned to the ground many 
times; it may have appeared as surface-water and again dis- 
appeared to great depths. It has been estimated that water 
moves in the ground at rates varying from 0.2 to 20 feet per 
day. This long contact with rocks will, of course, bring min- 
eral substances into solution which may be precipitated as 
new rocks are reached or other streams encountered, so that 
the same gallon of water may have had many stages in its 
course and may have held many different substances in solu- 
tion. An example of how much can be so held is found in 
the waters of the alkali belt (page 241). 

It is no wonder that so active a solvent as water should 
take with it much substance whenever it remains long in con- 
tact with soil or rock, for it may be many months before that 
which has once sunk out of sight again appears. In fact, great 
rivers are supposed to flow into the sea from under the sur- 
face. 

Then, too, the acquisition of dissolved gases favors the 
solution of many substances; for instance, water carrying 
carbon dioxide dissolves limestone as well as lead and cop- 
per, and when at low temperature and containing ammo- 
nium carbonate water may dissolve ferric iron. 

Water carrying organic acids dissolves among other sub- 
stances iron compounds which may or may not be in the 
ferrous condition, and therefore may or may not be precipi- 
tated on coming to the surface. And as we have seen that 
the ground below a certain level is permeated with moving 
water, whatever is buried in the earth is likewise liable to enter 
the watercourses in one form or another. 

An understanding of this movement of water under- 



66 AIR, WATER, AND FOOD. 

ground, with the accompanying changes in its character, 
cannot be too strongly insisted upon, for the lack of com- 
prehension of it is at the root of most of the troubles from 
well-waters. For example, the leaching cesspool, the primi- 
tive " septic tank," delivers its more or less filtered water rich 
in nitrogen compounds into the general circulation at a 
depth below the most efficient action of the nitrifying or- 
ganisms, hence it may permit the passage of organisms of 
putrefaction into underground streams or into the well, when 
access is direct. Even when filtration is perfect, the products 
of decay are yet carried with it and so tell the story of the 
past. The difficulty is to determine the state of the filter 
which may be on a neighbor's land many hundred feet away, 
and to be sure that its action is uniform. Experience with 
artificial filters shows how difficult it is to maintain efficiency 
with rapid use; hence heavy rains or wet years may cause a 
state of danger not ordinarily existing. 

The relation of water to human health must be consid- 
ered chiefly in the light of the changes which go on in the 
substances held suspended or dissolved in it, and the effect 
of these changes on the wholesomeness of the water. The 
suspended matter may be either inert, as clay or sand; dead 
vegetable, as fragments of plants; living vegetable, as plants 
floating on the surface, diatoms, desmids, a'gse, etc.; dead or 
living animal, as infusoria, small crustaceans, etc. 

Wherever these occur there are found the lower orders 
of vegetable organisms, fungi, moulds, bacteria, ready to do 
the necessary work of decomposition preparatory to solu- 
tion. The mere presence of these forms of living matter 
does not of itself mean danger to those using the water, but 
among these may be found pathogenic organisms which are, 
at present, considered as liable to cause disease. Such mi- 
crobes do not find in water a congenial habitat, and, fortu- 



water: source, properties, and relation to life. 67 

nately, do not thrive on the vegetable diet and in the cool tem- 
perature of natural waters, hence the other organisms soon 
overpower them; danger decreases not only in proportion to 
distance, time, and dilution, but also, probably, to the abun- 
dance of other vegetable life. Under favorable circum- 
stances the danger is, however, a very real one. 

The presence of certain living plants may, moreover, give 
rise to unpleasant, if not dangerous, tastes and odors, due to 
the presence of extremely pungent oils or other aromatic 
substances formed in the process of growth. When these 
plants are decaying putrefactive odors are also present, some- 
times rendering the water too offensive for use. These or- 
ganisms are described in Whipple's " Microscopy of Drink- 
ing-water," and in Chapter VII a short list of those which 
give characteristic odors will be found. 

The presence of much decaying vegetable matter in 
drinking-water is to be avoided, since it is not known what 
effect it may have upon the general health of the individual, 
rendering him perhaps more susceptible to disease. 

Food-supply is a necessary condition for life, and there 
cannot be abundant growth in a water without a correspond- 
ingly large amount of dissolved substances furnishing the food 
for this living fauna and flora. As has been stated, water 
usually carries considerable mineral substance and is often 
supplied with organic and gaseous compounds, while nitro- 
gen is furnished from many sources, most abundantly from 
sewage, so that it is not strange that water-life is so abundant, 
but rather that it is not more so. Most of the difficulties in 
securing a satisfactory water-supply are connected with the 
cycle of nitrogen in its relation to organic life. 

This may be briefly stated as follows: Nitrogen is found 
as an essential constituent of all living matter. When thus 
combined, it is the so-called organic nitrogen, and is found 



68 AIR, WATER, AND FOOD. 

in undecomposed vegetable or animal substances. As soon as 
dead, these substances may become food for micro-organisms 
and the nitrogen then appears in a form from which it can be 
obtained as ammonia; for instance, from decaying beans, from 
putrefying broth, and from fresh sewage. This process takes 
place with or without much air and may be accompanied by 
very bad odors. As soon, however, as the nitrogen has passed 
from the insoluble organic form into the soluble compounds 
from which ammonia is obtained, then, if oxygen is present, 
and only then, another set of micro-organisms take up the 
work and nitrites appear; when still another set have done 
their work the nitrogen is found only in combination as ni- 
trates, fully oxidized and mineralized, no longer organic or 
capable of sustaining the life of the lower forms of vegetation, 
but, on the other hand, the most valuable food for chlorophyll- 
bearing plants which convert nitrates again into organic 
nitrogen. This cycle may be arrested or broken at certain 
stages. If the soluble ammonia compounds are set free out 
of contact with air or below the layers of soil containing the 
nitrifying organisms, they may remain indefinitely un- 
changed. If nitrates have been carried below the reach of 
the roots of the chlorophyll-bearing plants, or if they are con- 
fined in a space deficient in oxygen, then an access of decom- 
posable organic matter with micro-organisms will cause a, 
reduction of the nitrates to nitrites and free nitrogen, through 
the action of these lower plants which, in the absence of 
air, take the little oxygen they need from mineral com- 
pounds. 

These micro-organisms are not the only ones at work, 
however. In any sudden prominence of one factor others 
are apt to be overlooked; thus in the present case the in- 
finitely small has so powerfully affected men's minds tha f r 
partly because the micro-organisms are beyond their range 



WATER: SOURCE, PROPERTIES, AND RELATION TO LIFE. 69 

of vision, such forms of life as are evident to the naked eye 
or with low powers of the microscope have been overlooked 
to an extent. 

As agents of putrefaction and of decay the micro-organ- 
isms have their work to do, but the final purification — the 
finishing up of the work — belongs to another order of life. 
The still minute but visible green plants — those which float 
free in water or attach themselves to larger growths — have 
now their part to play. The life-history of these forms has 
been little studied, and the work they do in the actual puri- 
fying of polluted water has been almost overlooked. The 
impression left on reading most books is that when foul mat- 
ter has been dissolved and converted into ammonia, carbon 
dioxide, and nitrates the work is done, but these compounds 
only furnish food for the next class, and these again for in- 
fusoria, tiny crustaceans, etc. 

In some cases these organisms succeed each other with 
great rapidity; in one case the fauna and flora of a given 
pond varied each week of a season, certain rare forms being 
found only once. 

There is needed, almost more than anything else, a con- 
secutive study of the green plants found in water-supplies, 
since by their cultivation greater purity might be attained 
and possibly a way might be found of exterminating the dis- 
agreeable ones. The most unexpected results may follow 
the long study of a single organism, such as has been given 
to Oscillaria prolifica of Jamaica Pond for a period of fifteen 
years. Weekly, sometimes daily, observations have been 
made for several years.* 

It is organisms of this class which give tastes and odors 
to water, and which, if enough were known concerning them, 

* Trans. A. A. A. S., 1898. Technology Quarterly, 14 {igoi) t 302; 15 
<{jgo2) y 308. 



JO AIR, WATER, AND FOOD. 

would probably give perfectly trustworthy evidence as to the 
past history or source of contamination. 

The two classes of organisms work in opposite directions, 
and so long as food is present for either, life will increase with 
proportional rapidity. This connection of cause and effect 
should be made familiar to the intelligent citizen. When a 
ground- water free from all organic matter but rich in 
nitrates is exposed in an open basin the rich growth of 
chlorophyll-bearing algae follows as a matter of course; later, 
decay sets in and products of decomposition abound, the air 
above being the source of a constant supply of spores of all 
kinds. 

When a house- or barn-drain empties into a small slug- 
gish stream, it soon becomes filled with green plants thriving 
on the ammonia, and it is often possible to trace the source 
of pollution of a large lake by the line of green anabaena 
leading to the insignificant ditch. 

A curious blindness on the part of managers of water- 
works to the movements of water and its action in transport- 
ing material is seen not only in the almost universal proximity 
of cemeteries to reservoirs, but also in the common practice 
of dressing the sloping banks of turf with a heavy coating of 
manure. Even if this was derived from clean stables and 
was not liable to be contaminated with night-soil, the abun- 
dant food for plants which inevitably finds its way into the 
reservoir occasions as fruitful results in the water as on the 
banks, and is undoubtedly the cause of much of the trouble 
in storage basins. 

It is evident, therefore, that a once polluted water cannot 
be said to be purified so long as food for green plants re- 
mains, for the moment the temperature and other conditions 
be^nf favorable growth will begin. The term "purifica- 
tion" f aken in a chemical sense, should not be looselv used. 



water: source, properties, and relation to life. 71 

Complete purification can take place only when all traces of 
former impurity, in any form, have been removed. Chemical 
precipitation of sewage leaves the soluble ammonia, and sand 
filtration leaves nitrates to serve for abundant life and sub- 
sequent decay in the streams into which the effluents flow. 
Such effluents are clarified and the organic matter may have 
been mineralized, but this is not purified water. Only when 
growing plants have removed this food and have themselves 
been removed can the water approach a purified condition. 

The effect of storage of water containing high nitrates 
in open tanks or reservoirs exposed to the collection of dust 
will be that spores of chlorophyll-bearing algae, diatoms, 
desmids, etc., will soon develop and will increase as long, as 
the food (nitrates, mineral matter, etc.) lasts. Only by pro- 
tection from dust and light can such water be kept free 
from unpleasant accumulations of suspended organisms or 
from disagreeable tastes. Unpolluted surface-waters, on the 
other hand, improve on storage, as a general rule, if the basin 
is a clean one. The storage of polluted or clarified water is 
thus forbidden, since not infrequently the first indication of 
the pollution of a surface supply is given by the appearance 
of some member of that richly nitrogenous group of algae 
called cyanophycecc, or " blue- greens," from the presence of 
blue or purple coloring matter along with the yellow-green 
chlorophyll. Since this group of plants contains from seven 
to eleven per cent, of nitrogen, while other groups contain 
only one or two, it is evident that, if it is to flourish, more 
nitrogenous food must be supplied. This may be derived 
from fertilized fields, from decay of other vegetable life, as 
well as from the richer source of direct sewage; but, in anv 
case, the growth of these plants is a sign of abundant food- 
supply which must be cut off if they are to be starved out, as 
they must be unless they are removed while fresh by strain- 



72 AIR, WATER, AND FOOD. 

ing or skimming, for the odor of their decay is so intolerable 
as to preclude the use of the water. In some cases the odor 
accompanying their growth renders the water quite objec- 
tionable, and neither natural nor artificial filtration is able to 
remove it. 

Either natural or artificial basins may have a collection of 
vegetable matter on the bottom which slowly decomposes 
in summer, and since the bottom water is colder, the resulting 
ammonia remains until the late fall overturn, when it is 
brought to the surface, where it favors the growth of diatoms 
and other cold-water plants. Certain diatoms, as asterio- 
nella, cause disagreeable odors. Such basins show the least 
ammonia in early October and the most in late November. 

In order to make any predictions as to the pro'bable de- 
velopment of this flora and fauna of water, experience and 
at least a year's watching of any given supply are required 
until more is known of the life-history of these forms of life. 
Nothing is more needed to-day than work along these lines. 
When may disagreeable odors and tastes be expected? 
What precaution or measures may be taken in each case to 
prevent them? These are the questions the water-works 
superintendent, equally with the consumer, is asking, for the 
most part vainly as yet. 

As has been stated, surface-waters often carry stable or- 
ganic matter in connection with color, so that while the 
organic nitrogen shows high, no free ammonia or nitrates are 
formed on standing. These weak meadow-teas are now 
largely used for town supplies, and a word as to the source 
of the color may not be amiss. Many carbonaceous sub- 
stances, sugar, for example, when partially broken up become 
caramelized and give a brown solution, the color being due 
to substances richer in carbon; this color is deeper as the 
decomposition is more complete. There is no reason to sup- 



water: source, properties, and relation to life. 73 

pose that such compounds have any deleterious effect on 
health. Indeed, experience has proved that such waters are 
more reliable than many others. 

The chlorine of unpolluted natural waters is derived from 
the sea in past or present times. Waves breaking on a 
rocky shore send finely divided salt-spray high into the air; 
dust-particles becoming coated with it carry their burden of 
salt around the world. The rain brings to earth now more, 
now less of this salted dust, each region receiving in the 
course of the year an amount fairly proportional to its dis- 
tance from the seacoast and to the rainfall. No mountain 
lake or stream has yet been found free from this element. 
Where evaporation and rainfall nearly balance, the normal 
chlorine will be that of the rain for the year, but where evapo- 
ration is in excess it may exceed that for any given year. In 
the absence of salt-springs and industries using much salt, 
the source of chlorine in excess of the normal is the do- 
mestic life of man. Mr. F. P. Stearns has estimated that the 
chlorine in the annual drainage of any watershed is increased 
one-tenth part per million by 20 inhabitants per square mile. 

Chlorine may serve to prove not only the presence but 
the amount of sewage pollution in any case where the other 
factors are known. Otherwise chlorine has no sanitary 
significance. 

Of the mineral constituents in waters there is little to 
say except that, like climate, water is to be taken as It is 
found — hard, high in mineral matters if derived from a lime- 
stone region, soft if from archean formations. Physicians are 
not agreed as to the effects of hard water, or of the brown 
soft waters. 

Fortunately the human system possesses remarkable 
adaptability, so that if slowly accustomed to a given condi- 
tion, as we have seen in the case of air, and as we shall have 



74 AIR, WATER, AND FOOD. 

occasion to remark when food is considered, it can safely 
bear what would be a serious shock if suddenly encountered 
from an opposite condition. Natives of a hard-water region 
are made ill on coming to a soft-water region, and vice versa. 
Inhabitants of a city with a polluted water-supply seem to 
acquire a certain immunity. 

The safety from organic contamination secured by the 
use of distilled water has brought up the question of a pos- 
sible danger in too little mineral contents for the best cellular 
interchange wherein lies life. 

With the superabundance of mineral salts in ordinary 
diet, there would seem to be little cause for alarm; but if the 
food were poor in these substances, it is quite conceivable 
that evil results might follow a free use of distilled water. 

A word as to the care of water in the house may not 
seem amiss, in view of the tendency it has to absorb gases, 
to collect dust, to favor chemical and vital changes, to dis- 
solve metals. 

Too great care cannot be taken in all these directions to 
secure water freshly drawn from the main pipe beyond the 
lead or brass house-pipes and to avoid thos,e traps for the un- 
wary householders — faucet filters. 

When the water-supply is cafe, but warm and flat to the 
taste, ice is frequently used to cool it. 

Much has been said about the dangers of ice when used 
in drinking-water and on or about food. The latter is prob- 
ably the most serious danger, since people are not so careful 
about the quality of ice for that purpose. 

Certain rules may be broadly stated as guides to the 
householder: 

Crystal-clear ice, free from crevices, bubbles, etc., is 
probably pure, for it has been formed from slow freezing in 
a thin layer, over a deep mass of water, as 20 to 30 inches of 



water: source, properties, and relation to life. 75 

ice in a pond 40 or 60 feet deep. In this case the impurities 
have been excluded. This crystal ice is impermeable to air 
and therefore to what air carries, and of course to water 
and what it carries. 

An equally safe rule is to discard all "snow-ice" made 
from snow saturated with water. 

The increasing difficulty of obtaining safe water has 
caused an increasing use of distilled water obtained either 
from domestic stills or in bottles or carboys from manu- 
facturers. The latter is often a desirable source of drink- 
ing-water if the glass does not scale off from the bottles. 
A very little common salt may be added if the consumer 
prefers, or even a drop or two of the druggists' "lime- 
water." 

The domestic still, if made from a poor quality of metal, 
may bring an evil second only to that of polluted water. 
Lead should not enter into its construction. 



CHAPTER VI. 

THE PROBLEM OF SAFE AND ACCEPTABLE WATER AND THE 
INTERPRETATION OF ANALYSES. 

{From the Chemist's Standpoint.) 

From what has been said it will be evident that the prob- 
lem of safe water for domestic use is not so much concerned 
with the water itself as with its property as a carrier and its 
part in chemical changes. 

We have seen how a great variety of vegetable and ani- 
mal matter finds its way into the water of a settled region; 
and as it is constantly being transformed from one form to 
another by the agency of multitudes of organisms, it is evi- 
dent that the exigencies of modern life render impossible the 
exclusive use of water of great organic purity. It is useless, 
therefore, to fight over again the battles of the past as to the 
source and kind of " organic matter " in water. 

We have also seen that it is not the mere presence of 
compounds of carbon, hydrogen, and nitrogen in drinking- 
water which gives the element of danger. It is not even 
the fact that these have taken part in animal life; fish and 
frogs continually die in ponds and streams, to say nothing 
of countless cyclops and mosquito larvae. Well authenti- 
cated cases are on record in which one drink of a polluted 
water has proved fatal; while, on the other hand, it is equally 
sure that highly contaminated water has been used with ap- 
parent impunity. 

76 



water: the problem of SAFE WATER. J7 

When water has received excreta of diseased human 
beings, disease-germs are very likely to be conveyed by it 
to other human beings. In a city there are. always cases of 
disease, therefore all city sewage is to be considered danger- 
ous. But besides the living germs there are other accom- 
paniments of decaying organic matter which, when in con- 
centrated form, sometimes show toxic properties. Certain 
facts and many conjectures lead to the conclusion - that a 
water is " safe " only when free from decaying substances. 

Along with the millions of harmless micro-organisms 
engaged in the work of conversion there may be a few score 
inimical to the health of man, and for the education of the 
still skeptical public it is often advisable to speak somewhat 
strongly of the possible dangers from water-borne disease- 
germs. -\ •„ 

Nitrogen as the Essential Element in Living Matter. — All 
organisms from the lowest to the highest thrive only in the 
presence of food; therefore only that organic, matter which 
serves to support life or which, as a product of life, may be 
deleterious to man is rightly to be held as dangerous. The 
element common to both kinds is nitrogen; therefore the 
water-analyst seeks evidence not only of its presence or ab- 
sence, but of the forms in which it is found and their relation 
to one another. It may be assumed that any water which 
shows no change in the relative amount of its nitrogenous 
compounds at the end of a week either does not contain the 
organisms necessary to effect this change or is wanting in 
the food upon which they can thrive. As, however, it is 
inconvenient to wait a week before deciding this point, other 
methods are used. The so-called a 1 buminoid ammonia is 
supposed to indicate the amount of decomposable nitrogen- 
ous matter, but, as a matter of fact, taken by itself it gives 
little information of value. While its absence is conclusive, 



j8 AIR, WATER, AND FOOD. 

its presence is not equally so; but a proof of its variability 
from- day to day is really valuable. Whether used in the final 
interpretation or not, " organic nitrogen " (or that portion 
of it appearing as albuminoid ammonia) is always deter- 
mined, together with the other forms, as soon as the sample is 
received. 

A nitrogenous organic compound is dangerous from one 
of two causes: first, because it is already decaying and har- 
bors pathogenic germs or is giving off toxines; or, second, 
because it will furnish food for a further development of bac- 
terial life. 

As to its derivation from animal or from vegetable mat- 
ter, there need be little discussion, especially since the recog- 
nition of the high nitrogenous content of the blue-green 
algae and the nitrogenous character of " soil-humus " and 
the close approximation of animal and vegetable protoplasm. 
But it is most important to know if it is stable, since one of 
the best aphorisms ever contributed to the literature of water- 
analysis is given by Dr. Drown's statement, " A state of 
change is a state of danger." 

Results of the Decay of Nitrogenous Organic Matter. — The 
products of the first stage of decay of this class of organic 
matter are carbon dioxide and ammonia. It is to the 
latter that we turn for the proofs sought, by reason of the 
methods at hand for detecting such small amounts as one 
part in a billion parts of water, and because it is for the nitro- 
gen compound that we seek. 

The mere presence of free ammonia is not a sufficient in- 
dication of recent pollution from human sources. Rain-water, 
as shown in Table III, contains considerable quantities; 
decaying blue-green algae furnish it in still larger amounts, 
and moreover it offers acceptab!e food to plant-life and may 
therefore disappear in the form of combined nitrogen. 



water: the problem of safe water. 79 

Nevertheless, it is to be held as one of the chief witnesses, for 
it is found in sewage in a thousand times the quantity in 
which it occurs in ordinary potable water. While putrefac- 
tive decay takes place by stages, the lines of division are not 
sharply drawn, and nitrites, the result of the second stage, may 
be and usually are found in polluted waters together with 
ammonia. So frequently is this the case that it is considered 
circumstantial evidence sufficient to convict when both am- 
monia and nitrites are found together. (See Tables V and 
VI, p. 241.) 

The reason is not far to seek. Both are not only prod- 
ucts of decay, but both are in that unstable condition which 
indicates active processes, and which therefore means the 
presence of micro-organisms. Certain exceptions will be 
noted later. 

The fourth form of nitrogen, that found in nitrates, is no 
longer classed as organic; it is now become food for green 
plants and cannot nourish the class to which bacteria and 
pathogenic germs belong, hence it is fair to presume that for 
lack of food the latter have succumbed or have been other- 
wise removed. The value of this test is the proof it sometimes 
furnishes of previous sewage pollution, since the nitrogen 
present in excess of that brought down by rain must have 
been furnished either by fertilizers, by decaying matter, or by 
sewage. (See Tables V and VI, p. 241.) 

Organic Carbon. — Since by far the largest constituent of 
organic matter is carbon, some fifty per cent., it might seem 
as if this was the best indication of pollution. Indeed, it was 
formerly so considered, and many methods have been de- 
vised to show its presence quantitatively. As our knowledge 
of the slight differences between many forms of animal and 
vegetable substances grows, the probability of any conclusive 
evidence from this source, either as to past history or present 



8o . AIR, WATER, AND FOOD. 

condition, decreases. In short, although for many years 
water-analysts have been striving to perfect methods of de- 
tecting certain substances and certain organisms, it would 
seem as if they were no nearer a discovery of one simple de- 
cisive test, but, in most cases, were driven to a somewhat 
elaborate examination in which one test only furnishes one 
link in the chain of evidence. 

Sanitary Analysis. — The examination of a water to deter- 
mine its safety for domestic use is called a sanitary analys's, 
in distinction from that examination which determines its 
fitness for manufacturing purposes, for use in steam-boilers, 
or its medicinal value. 

Four points are to be determined: First, the amount, if 
any, of organic matter in a living or dead condition, sus- 
pended or dissolved in the water; second, the amount and 
character of the products of decomposition of organic mat- 
ter, and their relative proportions to one another; third, the 
stability of the undecomposed organic substances; fourth, 
the amount of certain mineral substances dissolved. From 
these results we draw conclusions as to the present condition 
and past history of the water. These conclusions are not in- 
fallible, but there are enough unavoidable risks in human 
life without taking unnecessary ones; and if pollution is 
proved, the cause should be removed or the supply aban- 
doned. 

Preliminary Inspection. — So long as the eye can re-enforce 
the other tests and the whole course of the water may be 
clearly traced, it is comparatively easy to judge of the charac- 
ter of a supply and of its safety for human use; but when a 
hole in the ground is the visible source, or the actual history 
of the water is hidden in unknown distances and depths, the 
diagnosis is more difficult. 

First, the geological horizon and superficial soil must be 



water: the problem of safe water. 8r 

studied; the direction and flow of underground water, not the 
slope of the surface only; the possible sources of danger, 
occasional as well as constant, within at least a quarter of a 
mile radius. The composition of unpolluted water of the 
same region should always be at hand for consultation. 

Safe Water. — As has been said, we can no longer require 
pure water; the most that we can demand is that the supply 
shall be safe. To the uninitiated one sample of clear, color- 
less water seems very like any other. The safe, colored or 
muddy water of a stream or pond seems less desirable than 
the clear, cold water of a badly polluted well. 

A water may be normally safe and yet, from exceptional 
circumstances, be for a time a source of danger. In one case 
the mouth of a well at a factory was overflowed by a con- 
taminated brook raised above its usual level by a heavy 
shower for half an hour only. Some thirty cases of typhoid 
fever resulted, so close to one another and so suddenly ceas- 
ing as to leave no doubt of the fact that for only a few hours 
was the water unsafe. How, then, shall a chemist tell if at 
some past time a water may have been or at some future time 
may become a source of disease? Only by carefully weigh- 
ing all the testimony attainable — ocular, chemical, biological, 
bacteriological — in the light of past experience. 

The day of the vest-pocket sample, usually in a flavoring- 
extract bottle, cork and all, is nearly past, but that of the 
fruit-jar, with a sticky rubber ring and corroded zinc top, is 
still with us. That admiration for chemical knowledge and 
belief in chemical clairvoyance which expects the chemist to 
decide from a sample while you wait if a certain water caused 
the death of a person a month since in a distant town under 
unknown conditions is very trying to the man who knows his 
own limitations. 

The market value of an analysis cannot well be appre- 



82 AIR, WATER, AND FOOD. 

dated until a juster estimate of the professional training of 
the analyst is a part of common knowledge. 

Safe and Acceptable Water. — It is not enough that a 
supply shall be free to-day from disease-germs; it should re- 
main free from changes for a reasonable period of time. 
Therefore the advice desired by the towns seeking for sup- 
plies implies much more than mere analysis; it includes esti- 
mates of future changes, of variations due to possible further 
developments, and of the effect of these variations on accept- 
ability as well as safety. 

To be fully acceptable, a water should be free from color, 
odor, turbidity, sediment, and of a uniform temperature so 
low as to admit of use without ice. Only such water as has 
been earth-filtered and earth-cooled can meet this demand, 
but the supply of this class is becoming drawn upon to its 
limit; besides there are difficulties in the conveyance and 
storage of ground-water which offset many of its advantages. 

From the foregoing paragraphs it will be seen not only 
that waters carry every possible degree of safety or danger 
according to the country they drain, the num'ber and habits 
of the people living on the watershed, and the presence or 
absence of factories, slaughter-houses, etc., but that many 
elements enter into the judgment of a water-supply, and how 
different these elements are in different waters. Safe water 
is that which carries neither seeds of disease nor such sub- 
stances as are deleterious in any way to mankind in general. 

A brown water may yield 20 parts per million organic 
matter and show 10 parts oxygen consumed, and yet be a 
safe and wholesome water. A ground-water may show 5 
parts nitrates, and yet for ten or twenty years prove a safe 
supply. 

Since, however, water is so universally made a carrier of 
refuse, it is difficult to find a stream or well which fulfils the 



water: the problem of safe water. 83 

above exacting requirements, and a compromise is made 
which sets certain arbitrary limits and so keeps the chances 
small. Such limits are very misleading of themselves, espe- 
cially if used over a wide extent of territory. The English 
standards, for instance, are not applicable to eastern North 
America. Only a study of all local conditions and a wise in- 
terpretation of all results can make standard figures of any 
significance. This is true, also, of bacterial results in surface- 
waters. In the natural condition of lakes and streams there 
are so many varieties of bacteria present and in such varying 
numbers, according to wind and rain and watershed, that 
taken alone the numerical count gives no more convincing 
proof than is found in chemical figures. 

While it is quite within the limits of possibility that a 
culture-tube of typhoid bacilli might be emptied into the 
middle of a river or be washed into a reservoir, and chemical 
analysis give no sign, yet no continuous natural means of 
contamination is known which is not accompanied by sub- 
stances readily detected by suitable chemical examination. 
In either case an epidemic may or may not result, dependent 
upon causes other than the mere presence or absence of the 
micro-organisms. 

If drainage from a house or barn is seen entering a 
stream, it does not need a dozen plate-cultures to prove that 
there is possible danger. Such tests may, however, when 
used with skill, serve to trace contamination back to its 
source, and is another means at the service of the trained 
water-works superintendent whereby he can keep a close 
watch over the character of his supply. 

As a means of control of the efficiency of filter-plants the 
bacterial examination is invaluable, and as a knowledge of 
the forms which accompany pathogenic germs becomes more 
certain the value of these tests will increase, even if the 



84 AIR, WATER, AND FOOD. 

classification and identification is not perfected to scientific 
accuracy. 

It is one of the penalties of living in a large city that the 
water-supply must of necessity be surface-water which has 
been caught and stored at a distance or that which has been 
filched from a stream, filtered and made passable. Conse- 
quently education must take the place of instinct, and custom 
must make that acceptable which circumstances render 
necessary. 

THE INTERPRETATION OF ANALYSES. 

Experience in cutting through glacial moraines for rail- 
ways or in driving levels for mining operations does not 
qualify a man for exploration of a Babylonian or prehistoric 
mound. Human occupations have left upon the sand and 
clay evidences which, although so slight as to be unnoticed 
by the casual observer, are like an open book to him who 
patiently acquires a knowledge of the meaning of the dis- 
placements, discolorations, and enclosed fragments. Flowing 
water, like sand and clay strata, bears evidences of its previous 
history no less intelligible to him who has the key to the 
cipher and who adds to the keen eye of the detective and 
ready wit of the interpreter the sound judgment of the engi- 
neer. Reasoning upon insufficient premises will as often 
fail in the one case as in the other, while lucky guesses fre- 
quently encourage superficiality in both. 

After the analyst has entered on the blank (page 141) the 
six to ten records needed for a ground-water, or the fifteen 
to twenty for a surface-water; after the columns headed 
Bacteria, Diatoms, Algae, etc., have been filled in, there still 
remains the summing up of the case by the judge. The 
correct interpretation of results means a knowledge of 
the source, geological horizon, surroundings, probable 



water: the interpretation of analyses. 85 

changes, and the significance of each item in this particular 
case. Each class of water has its own characteristics. The 
presence, in quantity, of any given element is interpreted 
according to the kind of water under consideration. Spring- 
water is, of course, colorless; lake-water of equal safety is 
probably colored. Spring-water must be, as a rule, free from 
ammonia; lake-water may at times contain considerable 
amounts without detracting from its good character. 

Classification of Waters. — To facilitate examination, 
therefore, w r aters may be divided Into three classes: first, 
cistern, brook, pond, and river water — so-called surface- 
water; second, spring and deep-well water; and third, shal- 
low wells and sewage effluents. 

Water of the last two classes has been for greater or less 
periods of time in contact with rock and filtered through 
sand, hence is designated as ground-water. 

A few examples taken from the different kinds of water 
showing the varying conditions to which they are subjected 
may serve to make the rules of interpretation clearer. 

Surface-Waters. — When rain-water falls on slated or 
shingled roofs and is conducted into cisterns, it carries with 
it whatever deposits lave collected, the pollen of forest-trees 
or disease-germs from city slums many miles away; from 
metal roofs it takes either the metal itself or the pain" used 
to protect the surface. In all cases, lower forms of animal 
life, small insects, and soot from chimneys may be present. 
These foreign substances should be at once filtered out with- 
out allowing time for organic decay, unless there is an auto- 
matic device for wasting the first washings of the collecting 
surface. There are still substances in solution which would 
be better away; therefore the water is allowed to stand 
quietly in order that the changes may have time to take 
place — to ferment, as it is often technically expressed. After 



86 AIR, WATER, AND FOOD. 

this season of purification the water is again filtered and 
stored ready for use. There is usually color and a little am- 
monia, but rarely nitrates. The soluble meta's, if once pres- 
ent, still remain. It goes without saying that all such 
cisterns must be absolutely impervious to surface drainage. 
For lack of one or all of these precautions, cistern-water has. 
often been found to be contaminated from cesspools, from 
leaden or painted roofs, or from decaying organic mat er. 

Brook-water. — The rain that falls on mountain slopes of 
granitic or other insoluble rocks washes from them whatever- 
loose earth may have fallen there, and from the firmly fixed 
lichens the small insects and other animal forms which they 
harbor. These are transported in brooks to the lower lands 
where the organisms decay, the heavier earthy particles fall- 
ing out by the way. 

If the upland rocks and soil yield a portion of mineral 
salts to the water, it may come out clear and colorless even if 
it has not penetrated to an appreciable depth. 

The water from these forest brooks, after remaining im- 
pounded in a clean lake or reservoir, exposed to sunlight and 
air, often becomes the safest source of supply. As with cis- 
terns, so with reservoirs, filtration, natural or artificial, may 
take place previous or subsequent to storage, or both before 
and after. 

Lake or Mixed Water. — Lakes are fed by springs as well 
as by brooks, or by that portion of rainfall which passes a few 
inches below the surface, and is filtered before reaching the' 
main body. If the banks are sandy and uninhabited, the 
water will show good effects from this filtration; but if the 
seepage-water comes from a settled country, it will bring 
either ammonia or nitrates. The analysis will quickly show 
this if the water sample can be taken before it has mixed 
with that bearing the spores of plants which are fed by 



water: the interpretation of analyses. 8y 

nitrates. Often the very presence of these plants furnishes 
the proof sought. 

River-waters. — A large stream, especially a muddy one, 
may receive the drainage of half a dozen cities a hundred miles 
distant and yet not give conclusive evidence of dangerous 
contamination, while a small river with a rapid current may 
become unsafe from the presence of a few villages a dozen 
miles away. 

Northeastern America is so well supplied with uninhab- 
ited high lands for collecting-grounds, and with basins in the 
glacial drift for storage in natural or artificial lakes, that very 
few rivers need to be used after they have become polluted. 
The Merrimac and the Hudson are, however, so used. In 
other parts of the country the use of rivers is an increasing 
necessity, requiring municipal filter plants. 

From every point of view organic matter should be kept 
as far as possible out of running streams which may at any- 
time be needed for public supplies, or the natural purifica- 
tion by algae should precede the final filtration and storage. 
It is quite probable that this double treatment may be more 
frequently required as unpolluted water becomes more 
scarce. 

What the method of filtration shall be depends upon the 
character of the water, whether clear or turbid with clay, 
whether certainly polluted or only with a remote possibility 
of contamination. Each problem must be studied by itself 
without prejudice in favor of any one method. It is the re- 
sult which must be kept in mind, namely, the furnishing of 
safe and acceptable water to the community. 

Effect of tJie Storage of Surface-water. — In interpreting 
his results, the analyst should take into acccunt the influence 
which the keeping of water in basins has upon its character. 
Storage of surface-water is of utmost importance in all cases- 



gg AIR, WATER, AND FOOD. 

of doubt. Most disease-germs find such water an unfavor- 
able medium for prolonged life, since exposure to sunlight 
soon destroys the darkness-loving bacteria, and a certain 
sterilizing effect results from the growth of green alg?e, so 
that water considerably polluted becomes purified if given 
time for the various agents to do their work; but time is 
essential. 

Odors. — For surface-waters one of the links in the chain 
of evidence is found in the odor, cold and hot, which to the 
trained and sensitive nose often gives convincing testimony. 
A musty odor, unmistakably different from a mouldy vege- 
table smell, betrays sewage contamination even when the 
chemical analysis might not be convincing. This odor is not 
always taken out. by filtration, neither is that of certain or- 
ganisms growing in stored water, notably Anabcena and 
Synurd. A study of these organisms is invaluable to the 
routine observer who watches the seasonal and annual 
changes in his reservoir. 

Turbidity and Sediment. — The determination of turbid- 
ity and sediment, added to the odor, tells much to the expert, 
but very little to the inexperienced student. Turbidity may 
be due to drainage contamination, to growth of bacteria, to 
clay, to iron, to swarms of micro-organisms. Sediment may 
be sand, zooglea, fragments of plants or animals, or ferric 
oxide. 

Filtration. — The subject of filtration has been so exten- 
sively treated elsewhere that the student is referred to the 
bibliography on page 263. There are cases in which it is 
preferable to run the risk of too much alum in the drinking- 
water, and too much sulphuric acid in boiler feed-water, 
rather than of too many micro-organisms with the accom- 
panying organic matter. 

It will have been noticed that the ideal natural water is 



water: the interpretation of analyses. 89 

that which has been earth-filtered, and thus all suspended 
matter, including microbes, has been removed. This sup- 
poses that sufficient time has elapsed so that all decomposing 
organic matter has been destroyed. Man tries to imitate 
nature's processes, but expects to accomplish it in moments 
instead of months. 

The era of house-filters, those admirable culture-grounds 
for bacteria, is happily nearly past. Taxpayers are becoming 
convinced that a good original water-supply in competent 
hands is worth paying for. Where straining only is needed, 
a flannel bag washed daily is as efficient as any faucet-filter. 
If the latter takes out color as well, it should be closely 
watched. Water should not be first boiled and then filtered, 
but first filtered and then boiled. 

Summary. — Surface-water. — In general it may be said 
that the waters of the first class found in New England are 
generally more or less colored, and contain more or less sus- 
pended organic life and its debris, which often impart a de- 
cided odor to the water. These waters, draining for the most 
part wooded and sparsely populated regions, are low in free 
ammonia, nitrates, and nitrites; low, also, in mineral salts, 
and with only a slight excess of chlorine over the normal. 
They are usually high in organic matter and albuminoid am- 
monia even when entirely free from pollution. 

In other parts of the United States surface-waters may be 
low in color, but with much suspended clay and silt, and may 
hold in solution notable quantities of mineral salts. The 
latter aid greatly in the clarification by artificial filtration, 
which is so often rendered necessary by the excessive turbid- 
ity even if not by sewage contamination. 

In Table IV, page 239, will be found examples showing 
at a glance how profoundly the character of a water is affected 
by the geological horizon, whether its source is in the glacial 



90 AIR, WATER, AND FOOD. 

drift of the Appalachian region, or in the limestone of the 
Hudson River Valley, or in the saline deposits of the sub- 
sided areas. 

Deep Wells and Springs. — The waters of the second class 
are derived from the depths of the earth, far below any pos- 
sible surface contamination, and have long been imprisoned 
in the dark and cold, and often subjected to great pressure, 
The influence of pressure on organisms has not been entirely 
worked out, but from what is known it is probably very un- 
favorable to the life of the lower organisms. The results of 
many bacterial examinations have been vitiated by the diffi- 
culty of securing a sample from great depths without con- 
tamination by surface exposure — pipes open to the air har- 
boring many forms of life. 

Deep wells, 700 feet and more, are not likely to be dan- 
gerous. They may often contain ammonia from prehistoric 
coal-fields or tertiary deposits, but rarely nitrates. This is 
accounted for by the fact that " the result of the changes of 
the nitrogenous organic substances which fall into the earth 
is, without doubt, frequently the formation of gaseous nitro- 
gen." Also, that " salts of nitric acid on penetrating into 
the depths of the earth give up their oxygen." * 

Owing to their long sojourn in the depths of the earth, 
these waters are higher in mineral substances than surface- 
waters. Since their origin is unknown, the chlorine cannot 
be correctly gauged, especially as there are saline waters deep 
down in rock cavities in all parts of the world. 

It is usually believed that these deep wells furnish a safe, 
palatable water when the kind and amount of mineral matter 
is not objectionable. 

Shallow Wells. — It is not to be wondered at that waters 

* Mendeleeff : "Chemistry," p. 223. 



water: the interpretation of analyses. 91 

of the third class — ground-water, taken from just beneath 
the surface layers of the soil — should contain many sub- 
stances foreign to the waters about them as well as to those 
at greater depths. The shallow wells, which are practically 
more or less diluted sewage effluents, present the greatest 
variety. They may be clear and colorless and show as great 
organic purity as the best mountain spring. In other cases, 
the overworked filter permits the passage of organisms and 
undecomposed material. In either case there will be found 
those compounds which, being soluble and stable, are car- 
ried with the water as signs to be read by him who knows the 
language. A complete history of each specimen of this class 
of ground-water is desirable, and with sufficient patience 
and care it may be obtained with reasonable accuracy, if the 
principles governing the circulation of water and the changes 
of the organic matter it carries be kept well in mind. 

It is certain at once that absence of color, of organic mat- 
ter in any form, and of odor should be insisted upon, for 
ground-water is filtered water and the filter should be doing 
its work. 

A modicum of geological knowledge is essential, as the 
presence of shaly or slaty rock will permit the passage into 
underground water of surface drainage with less purification 
than will a granite or sandstone region. A clayey soil is a less 
efficient filter than a sandy loam and permits the pollution 
to travel farther. 

Nitrogen in Well-water — It may be taken as an axiom 
that the only form of nitrogen permissible in a good ground- 
water is that of nitrates, a fully oxidized or mineralized food 
for green plants. If nitrites are also present, a source of 
pollution is at hand, for, as has been said, nitrites indicate 
either a stage of oxidation not completed or one of reduction 
from nitrates in the presence of organic matter. If free am- 



92 AIR, WATER, AND FOOD. 

monia be present, it is safe to say that the source is not only 
near but in actual contact, since but a few hours' time is 
needed to oxidize the ammonia in any soil not waterlogged. 
It may also be pretty safe to assume that bacteria are present, 
since ammonia is the first stage of that decomposition which 
they accompany. It is the part of prudence, therefore, to 
avoid any water which contains both free ammonia and 
nitrites above .200 or .300 parts per million of the first, and 
.020 or .030 of the second. 

The absorption of nitrogen by plants is rarely complete, 
so that it usually appears in far larger quantities in contami- 
nated ground-waters than could be obtained from purified 
rain-water. The leaching cesspool discharges its liquid con- 
tents below the zone of green-plant life; fertilized soil also 
yields a portion of its food value to the lower layers. A 
small portion of the nitrogen of vegetable origin may appear 
as nitrates, but only as a derivative of soil rich in humus is it 
likely to play any considerable part. In eastern America 
nitrates above 0.5 parts per million would arouse suspicion, 
;and above 5 parts would in most cases prove previous por- 
tion. 

It is evident that in the use of nitrogen as an indicator of 
the conditions of a water we are limfted, by the changeful 
character of the compounds, to certain not-to-be-mistaken 
amounts, and that in the majority of cases the evidence given 
is not decisive. v 

Chlorine in Well-water. — Fortunately there is another ele- 
ment not so eagerly sought for by plants and not liable to so 
many transformations. Thanks to the great solubility of its 
common compounds and to their stability, chlorine, once a 
constituent of a given body of water, is not extracted there- 
from and remains as a telltale to reveal the past history of a 
stream or spring. If a man is judged by the company he 



./? J 



vnt 



y># 




STATE BOARD OF HEALTH 
MAP OF THE 

STATE OF MASSACHUSETTS. ^^£^1 

SHOWING The ** 

NORMAL CHLORINE. 



WATER: THE INTERPRETATION OF ANALYSES. 93 

keeps, much more a water-supply. From sewage all the 
nitrogen may be removed and the chlorine still remain. 

But in order to use this information with any degree of 
certainty the normal chlorine of the locality must be known. 
If a map showing isochlors has been made of the region or 
State, and if there are no geological deposits to interfere, this 
is easy; but if the chemist or engineer has an unknown coun- 
try to report upon, it will be necessary to examine the local 
conditions and to choose six, eight, or ten samples of prob- 
able freedom from contamination and to test them for com- 
parison. The sources of the excess of chlorine over the 
normal are usually the sink-drain with its burden of salted 
water from domestic operations; the house-drain, with its 
chlorine-containing excreta; and the stable-drain, with a 
slight chlorine content in comparison with the other two. 

Mineral Substances. — Since water Is a universal solvent, 
it is not surprising to find considerable amounts of mineral 
matter in the two columns " Total Solid Residue on Evapo- 
ration " and " Hardness." How much calcium sulphate or 
magnesium chloride or other soluble mineral is allowable in 
a potable water is for the physician rather than the chemist 
to say. As has been said, the human system possesses great 
adaptability, not only for different foods, but for mineral sub- 
stances water-carried. Not so the steam-boiler or the laundry- 
tub, which reacts very sensitively and affects the pockets 
of the consumers. In a region of soft water, high solids 
with chlorine and nitrates indicate sewage pollution. 
Silica is much more commonly present even in surface- 
waters than is often supposed. What its effect may be is 
unknown. Iron is not uncommonly found in combination 
with organic matter in either surface or imperfectly filtered 
waters in contact with soils poor in calcium salts. It is fre- 
quently accompanied by free ammonia, which causes an 



94 AIR, WATER, AND FOOD. 

abundant growth of Crenothrix. It is also present in deep 
wells in the form of carbonate, which precipitates on exposure 
to warm air. 

In a considerable number of cases of public water-supply 
there is a mixture of surface and ground water which com- 
plicates the verdict, requiring a most delicate balancing of 
probabilities. The mineral contents often aid in this deci- 
sion. Well-waters, too, are often exposed to surface-wash 
because of poor protection at the mouth. Cyclops or other 
surface-water organisms often indicate this. 

Water-pipes. — After all, if the pipes conveying the water 
are of lead or brass, an additional danger appears. Gen- 
erally speaking, the purer the water the greater the risk. 
No common metal seems to withstand the action of soft 
water; six to eight years being the average age of galvanized 
pipe, and eight to ten of iron pipe. It would seem as if 
wooden pipe must come into greater use until some kind 
of glass is invented which will withstand this corrosive 
action and yet admit of plumber's connections. 

Value of Tests. — It is often asked if some tests cannot be 
made by the ordinary person of average intelligence which 
will enable him to tell the quality of a water as well as the 
expert to whom he pays ten or twenty dollars for an opinion. 
A careful perusal of the preceding pages will have answered 
the question in the negative. There is no assay of water as 
there is of gold and silver. Not one but ten or twenty tests 
must be made. Not only must the tests be made with the 
utmost care and cleanliness of person, utensils, and room, but 
the results must be studied in the light of other experience 
and other knowledge, geological and biological, and after 
all this is done there is an array of circumstantial evidence 
which must be carefully weighed by one whose judgment and 
experience enable him to read clearly where another might 



water: the interpretation of analyses. 95 

see nothing. The value of a water-analysis is in direct pro- 
portion to the knowledge and experience of the one who 
interprets it. Clinical skill in addition to theoretical knowl- 
edge is required to interpret the figures obtained in the course 
of a water-analysis, as in the symptoms of a disease: and the 
analogy goes still further, for as some diseases are clearly 
defined, others are so complicated that only those who have 
had long experience can outline a safe course, of treatment; 
so some waters bear the marks of their character so plainly 
as not to admit of mistake, while others require most careful 
study. For these reasons the value of water-analysis should 
not be decried because the fears aroused by reports given by 
unskilled analysts prove groundless, any more than the prac- 
tice of medicine should be discarded because inexperienced 
men make mistakes. 

Is the water in any given case safe for drinking? To an- 
swer this question there is needed a knowledge wider than a 
chemist's of the relation of decaying organic matter and of 
the germ-carrying power of water to outbreaks of disease. 
There must be added the knowledge of the biologist, the en- 
gineer, and the sanitarian. 



CHAPTER VII. 

ANALYTICAL METHODS.* 

General Statements. — Water-analysis cannot be carried on 
in an ordinary laboratory. In order to obtain satisfactory 
results it is necessary to have a room set apart for the pur- 
pose, and to exclude rigidly all operations which tend to the 
production of fumes or dust. Where such minute traces of 
substances are dealt with as in water-analysis, too much care 
cannot be taken to insure the absolute cleanliness of the ap 
paratus and the surroundings. It is desirable that the room 
be well lighted, and if possible the windows should face 
toward the north. 

The methods for the examination of water which are de- 
scribed in this chapter by no means comprise all that are in 
use. The directions are given for the use of students in our 
own laboratory under the conditions obtaining, i.e., of large 
classes and of several courses of study, with especial reference 
to educational rather than purely technical needs, and in some 
cases, no doubt, the traditions of thirty years may have unduly 
persisted. The methods have been so selected as to intro- 
duce a variety of apparatus and to illustrate principles. They 
have also been subjected to a thorough test in meeting the 
demands of practical work. 

Collection of Samples.— -F or the collection of water sam- 
ples, glass-stoppered bottles of about a gallon capacity are 
best. Those used in this laboratory are of white glass, fifteen 
inches high to the top of the stopper, five and a half inches 

* See Report of Committee on Standard Methods of Water-analysis, Jour, of 
Infectious Diseases, Supplement No. I, May, 1905. 

96 



water: analytical methods. 97 

in diameter, and weigh about three pounds. They have flat,, 
mushroom stoppers, on which is engraved a number to corre- 
spond with that on the bottle. The bottles, before being 
sent out, are thoroughly cleaned with potassium bichromate 
and sulphuric acid, washed with distilled water and dried. If 
glass-stoppered bottles are not at hand, new demijohns fitted 
with new corks may be used. A glass bottle or a demijohn 
is much to be preferred to an earthenware jug, because, if for 
no other reason, it is so much easier to be sure that the interior 
is clean. It should always be borne in mind that in water- 
analysis the question is one of very minute quantities of mate- 
rial, and that the methods to be employed are extremely 
delicate. Hence, in the case of many waters, careless hand- 
ling of the sample would contaminate the water to a sufficient: 
extent to render valueless the results obtained in the labora- 
tory. In collecting samples, the following directions should 
be closely followed: * 

Directions for Collecting Samples for Analysis — From 
a Water-tap. — Let the water run freely from the tap for a 
few minutes 'before collecting the sample. Then place the 
bottle directly under the tap and rinse it out with the waler 
three times, pouring out the water completely each time. 
Place it again under the tap; fill it to overflowing and pour 
out a small quantity so that there shall be left an air-space 
under the stopper of about an inch. Rinse off the stopoer 
with flowing water; put it into the bottle while still wet and 
secure it by tying over it a clean piece of cotton cloth. Seal, 
the ends of the string on the top of the stopper. Under no 
circumstances touch the inside of the neck of the bottle or 
the stem of the stopper with the hand, or wipe it with a 
cloth. 

From a Stream, Pond, or Reservoir. — Rinse the bottle and. 

* Ann. Rep. Mass. State Board of Health, 1890, p. 520. 



98 AIR, WATER, AND FOOD. 

stopper with the water, if this can be done without stirring | 
up the sediment on the bottom. Then sink the botlle, with 
the stopper in place, entirely beneath the surface of the water 
and take out the stopper at a distance of twelve inches or 
more below the surface. When the bottle is fu 1 replace the 
stopper, below the surface if possible, and secure it as directed 
above. It will be found convenient, in taking samples in 
this way, to have the bottle weighted so that it will sink be- 
low the surface, and to remove the stopper by a cord. It is 
important that the sample should be obtained free from the 
-sediment at the bottom of a stream and from the scum on 
the surface. If a stream should not be deep enough to admit 
of this method of taking a sample, dip up the water with an 
absolutely clean vessel and pour it into the bottle after the 
latter has been rinsed. 

The sample of water should be collected immediately be- 
fore shipping by express, so that as little time as possible 
shall intervene between the collection of the sample and its 
examination. All possible information should be furnished 
•concerning the source of the water and of possible sources of 
contamination. For example, in the case of a well, the prox- 
imity of dwellings, cesspools, or drains should be recorded, 
and the character and slope of the soil, whether toward or 
away from the well, should be noted. In the case of a sur- 
face-water, mention any abnormal or unusual conditions; as, 
for instance, if the streams or ponds are swollen by recent 
heavy rains, or are unusually low in consequence of prolonged 
drought, or if there be a great deal of vegetable growth in or 
on the surface of the water. Record, in short, any circum- 
stantial evidence which by any possibility may aid in the final 
judgment. 

The question of proper collection of samples is an impor- 
tant one, and the chemist is perfectly justified in refusing to 



water: analytical methods. 99 

give an opinion in regard to the purity of a water which he 
has not himself collected. The ignorance and carelessness 
shown by people who send samples for analysis are often- 
times quite amusing. Samples have been received at this 
laboratory in almost every kind of container imaginable, from 
an imperfectly rinsed whisky-bottle to a discarded syrup-jug, 
with about an inch of maple sugar in the bottom. One sam- 
ple was sent all the way trom Georgia in a stone jug with a 
corn-cob inserted for a stopper. Others are received with 
the stopper carefully (?) protected by a mass of sealing-wax 
or candle-grease. A favorite way is to send the sample in a 
fruit-jar packed in sawdust or straw. Opinions evidently 
differ greatly, too, in regard to the size of sample that is 
needed. It is no uncommon occurrence to have a person 
come into the laboratory with the remark, " Here is a sample 
of water that I want analyzed," supplemented by the produc- 
tion from a coat-pocket of a homoeopathic vial or a sample 
of half a pint or so of water. Of course, in cases like these 
practically nothing can be done. 

Preparation of the Sample for Analysis. — Since changes 
in the composition of a contaminated water are constantly 
going on, the analysis of the sample should be begun without 
•delay. The bottle is held under the tap, and the neck and 
stopper are washed free from adhering dust. The stopper Is 
rinsed off with some of the water from the bottle. Qualita- 
tive tests should be made for ammonia, nitrites and chlorine. 
With waters containing much suspended matter, and in the 
case of surface-waters in which it is desired to distinguish 
between the organic matter in solution and that in suspen- 
sion, a portion of the water should be filtered. In most 
cases the suspended matter can be removed by filtration 
through paper. For this purpose only the best Swedish 
filter-paper should be used, and the filters should be first 



IOO 



ATR, WATER, AND FOOD. 



thoroughly washed with ammonia-free water. With some 
waters containing very finely divided clay in suspension, fil- 
tration through paper will not be satisfactory, and the sample 
must be filtered by suction through a cylinder of ung'azed 
porcelain, such as an ordinary Chamberland-Pasteur hi er- 
tube. In the filtered water it is customary to determine the 
dissolved solids, the albuminoid ammonia, or the organic 
nitrogen, and the color. 

Determination of Free and Albuminoid Ammonia — 
Apparatus* — The apparatus used for the determination of 

ammonia is that shown 
in Fig. 8. It consists 
of a round-bottomed 
flask of 900 c.c. capaci- 
ty, with square shoul- 
ders and a narrow neck 
five inches long, and an 
ordinary Liebig con- 
denser fitted with an. 
inner tube of block tin,, 
3 / 16 of an inch in diame- 
ter. The flask is closed 
by a cork carrying a 
glass tube bent nearly at 
right angles, which 
slips for some distance 
within the tin tube cf 
the condenser. A tight 
joint is made by means 
of a large cork, which 
is shown in section in 
Fig. 9. The large cork 
serves the double purpose of making a tight joint with the 




ScaleJHin.= lfoot. 
Fig. 8. — Apparatus for Ammonia Dis- 
tillation. 



* A. H. Gill : /. Anal, and App. Chem., 6 {1892), 669. 



WATER: ANALYTICAL METHODS. 



IOI 



condenser and also as a convenient means for handling- the 
small glass tube. In order to remove the cork from the dis- 
tilling-flask, the glass tube carrying it is simply turned to one 
side, using the large cork as a pivot. The flasks are heated 
with the free flame of a Bunsen burner. 

New flasks are treated with boiling dilute sulphuric acid 
and potassium bichromate before they are used. New corks 
should be steamed out for one or two hours. A good, sound 
cork will last for several months with daily use. The dis- 



ssssssssssssssssssss/ss/.'/ . n - 




"~-.^'"-~~ ■ - , ■— 7-.,./. , ' — 



CORK JO I NT 

Full Size 

Fig. 9. 

tillates are received into small 50-c.c. flasks and poured into 
Nessler tubes for nesslerization. The Nessler tubes are 11 
inches long and f-inch internal diameter, the 50-c.c. mark 
being about two inches from the top. It is desirable to so 
arrange the apparatus as to collect the distillates directly in 
the Nessler tubes and at the same time render the apparatus 
more compact by having several condenser tubes run through 
a common cooling tank. For class work, however, the appa- 
ratus just described has been found most suitable. 

Directions. — Free the apparatus from ammonia by dis- 
tilling off the water in the flask, testing each 50-c.c. portion 
of the distillate until no color is given with the Nessler re- 
agent. When the distillate is free from ammonia, pour the 



102 AIR, WATER, AND FOOD. 

water left in the flasks into the bottle marked " Ammonia- 
free residues." 

Shake the bottle thoroughly to mix the sample. For 
determining the ammonia measure out in a calibrated flask a 
portion, usually 500 ex., the amount taken depending upon 
the result of the qualitative test. Pour this into the distilling- 
flask, and distil over three portions of 50 c.c. each into Nessler 
tubes or into the graduated flasks. 

In dealing with sewage or sewage effluents, which are very 
high in free ammonia, if the ammonia were collected in three 
portions, so much would distil over in the first portion that 
the color given with Nessler's reagent would often be too deep 
to read or a precipitate might form. To avoid this the total 
distillate of 150 to 175 c.c. is collected in a 200-c.c. graduated 
flask, made up to the mark, thoroughly mixed by pouring, and 
then 50 c.c. of it taken for nesslerization. In this way the 
ammonia is distributed more evenly in the distillate and the 
determination is not sacrificed. 

Notes. — When the amount of ammonia shown by the quali- 
tative test is high — i.e., shows a color equivalent to I. c.c. of the 
standard ammonia solution — a less quantity than 500 c.c. should 
be taken for the distillation, 100 c.c. or, in the case of sewage, 
even 10 c.c. being diluted to 500 c.c. with water free from 
ammonia. Sewage and soils may be distilled with steam in 
the apparatus figured on page 106 under the Kjeldahl pro- 
cess. 

After the free ammonia has been distilled off, allow the 
contents of the flask to cool slightly; then add 40 c.c. of alka- 
line permanganate through a funnel, taking care that none of 
the alkaline soluion touches the neck of the flask, and proceed 
with the distillation of the albuminoid ammonia; that is to 
say, the determination of the nitrogen of the undecomposed 
organic matter. With colored surface-waters distil off five 



water: analytical methods. 103 

portions of 50 c.c. each; with waters of low organic content 
three or four portions will suffice. 

In order to obtain about one half the total organic nitrogen 
regulate the height of the flame so that the time of distilling 
50 c.c. shall not be more than eight and not less than five 
minutes. 

It is impossible to convert all of the organic nitrogen into 
ammonia by boiling with alkaline permanganate. The amount 
of ammonia which is thus obtained depends not only upon the 
character of the substances, but also upon the concentration 
of the solution and the rate of boiling. In order that the 
albuminoid ammonia in potable waters shall bear some definite 
relation to the total organic nitrogen, it is necessary that these 
conditions shall be duplicated as nearly as possible in different 
determinations; that is, the alkaline permanganate must be 
added to a definite volume of the water, and the boiling must 
be carried on at a definite rate. Some of the highly colored 
surface-waters give up their nitrogen very slowly by this treat- 
ment; polluted waters, on the other hand, yield the ammonia 
more rapidly, so that the observation of the relative amounts 
found in the successive portions is of the utmost importance 
in forming a judgment. 

Have the Nessler tubes clean and thoroughly rinsed with 
ammonia-free water. Unless permanent standards are used 
prepare standards by adding to Nessler tubes nearly filled. 
with ammonia-free water varying quantities of the standard, 
ammonium chloride solution; for instance, 0.1, 0.3, 0.5, 0.7, 
1.0, 1.3, 1.5, 2.0, 2.5, 4.0, 6.0 c.c. The standard ammonium 
chloride solution contains .00001 gram N in one cubic centimeter. 

Mix the contents of the tubes by rotating them between 
the palms of the hands (never shake them like a test-tube or 
stir them with a rod), allow them to stand for two or three 
minutes, and add 1 c.c. of the Nessler' s reagent to the whole 



io4 



AIR, WATER, AND FOOD. 



set, and to the samples to be tested, as rapidly as possible. 
At the end of ten minutes match the colors and record the 
amount of ammonia. 

As an example of a colored surface-water may be given 
the following results from distilling 500 c.c: 





Free Ammonia. 


Albuminoid A 


mmonia. 


1st 


50 C.C, 


0.7 C.C. 


1st 50 c.c, 


4.5 c.c 


2d 


50 C.C, 


0.3 C.C 


2d 50 c.c, 


2.8 C.C 


3d 


50 C.C, 


0.0 c.c. 


3d 50 c.c, 
4th 50 c.c, 
5th 50 c.c, 


1.5 C.C. 
1.0 C.C 
0.5 c.c 



1.0 c.c. 10.3 cc. 

In this case the free ammonia would be 0.020 and the 
albuminoid ammonia .206 parts per million. 

In the case of water from suspicious wells and of sewage 
effluents, about 0.5 gram of freshly ignited sodium carbonate 
should be added before distillation, in order to make sure that 
the reaction of the water is not acid, and to decompose any 
urea which may be present. This will not be necessary with 
ordinary surface-waters, as experience has shown that they 
almost always have a slight alkaline reaction. 

A depth of color given by 6 c.c. of the standard ammonium 
chloride with the Nessler reagent is about the limit of satis- 
factory comparison in the 11-inch 50 c.c. tubes. The color 
given by 10 or 12 c.c. of the standard may be matched in the 
100 c.c. tubes with a depth of 5 inches and a diameter of ij 
inches. 

For most cases where great exactness is not essential it is 
possible to divide the 50 c.c. or the 100 c.c. into two equal 
parts by pouring into a tube the exact counterpart of the 
standard tube and matching the color. It is even possible to 
closely approximate the correct result by the use of a foot rule. 
The standard is, we will assume, 5 c.c. The height of liquid in 



water: analytical methods. 105 

the tube to be tested, we will call 9 inches. If the height of 
the column left which matches 5 c.c. is 3 inches, then the reading 
was 15 c.c. of the standard. 

The limit of solubility of the mercur-ammonium iodide is 
reached at 25 or 30 c.c. of the standard in 50 c.c. The incipient 
precipitate not only changes the color of the solution but causes 
a slight milkiness or turbidity which prevents a sharp reading 
of the color. 

The test is an excellent example of quantitive color work 
when carried out under strictly comparable conditions. 

It should perhaps be stated that in both the ammonium 
and nitrite determinations, as also in that of iron, dilution of 
the sample in which the color is already developed does not 
give a correct result. Therefore dilution if necessary must be 
made before the reagents are added. 

In order to secure the most accurate results it is impor- 
tant that the temperature of the distillates to be nesslerized 
and of the standards be the same, since the warmer solutions 
give a more intense color with the Nessler reagent. 

The compounds produced by the action of ammonia on 
mercuric solutions are considered as substitutions of 1 Hg 
for 2H in NH 4 , and are called mercur-ammoniums. Tetra- 
mercur-ammonium iodide (NHg 2 I), the compound formed by 
addition of the Nessler reagent, is a brown precipitate, sol- 
uble in excess of KI in the presence of KOH with a brown- 
ish-yellow color proportional within certain limits to the 
amount of NH 3 : 

NH 3 + (2HgI 2 + 2KI + 3KOH) = NHg 2 I + 5KI + 3H2O. 

The " free ammonia " in all probability does not exist in 
the water in a free state or as the hydroxide; it is probably 
present in the form of carbonate or of chloride. When water 
containing these or similar compounds of ammonia is boiled, 
they are decomposed and free ammonia passes off with the 



io6 



AIR, WATER, AND FOOD. 



steam and is found in the distillate; hence the origin of the 
name. 

Determination of Total Organic Nitrogen by the 
Kjeldahl Process — Directions. — Measure 500 c.c. of the 
water into a round-bottomed flask of 750 c.c. capacity and 




Fig. 10. — Apparatus for Distilling Ammonia by Steam. 



boil until about 200 c.c. have been driven off. (The free 
ammonia which is thus expelled may be determined, if de- 
sired, by connecting the flask with a condenser.) Allow the 
water remaining in the flask to cool, and add 10 c.c. of 
pure concentrated sulphuric acid free from nitrogen. Mix 
by shaking; place the flask in an inclined position on wire 



WATER. ANALYTICAL METHODS. IO7 

gauze under the hood and boil cautiously until the water is 
all driven off. Place a small funnel in the neck of the flask 
to prevent the escape of acid fumes, and continue the heating 
for at least half an hour after the sulphuric acid becomes 
white. Meanwhile rinse out the distilling apparatus (see 
Fig. 10), and free it from ammonia as usual. Then, after the 
acid in the digestion-flask has cooled, rinse down the neck 
of the flask with ioo c.c. of ammonia-free water and attach 
the flask to the distillation apparatus. Add ioo c.c. of 
potassium hydroxide solution through the separatory funnel 
and distil off the ammonia by steam, receiving the distillate 
in a 250-c.c. graduated flask. Conduct the distillation rather 
slowly until the first 50 c.c. have distilled over, then distil 
more rapidly until about 175 c.c. have been collected. Make 
the volume of the distillate up to 250 c.c. with ammonia-free 
water, mix it thoroughly and take 50 c.c. for nesslerization. 

Notes. — The principles involved in the method consist in 
the oxidation of the carbon and hydrogen of the organic mat- 
ter by boiling sulphuric acid, the nitrogen being converted 
into ammonia and held by the acid as ammonium sulphate. 
The ammonia is then liberated and distilled off. from an alka- 
line solution. The use of mercury and of. potassium per- 
manganate to assist in the oxidation has been found to be 
unnecessary, as the organic matter in natural waters is much 
more easily oxidized than in other substances,- — flour, for in- 
stance. The presence of nitrates and nitrites in waters has 
not been found to interfere with the accurate determination 
of the organic nitrogen. The error which has been found by 
Kjeldahl and Warrington to be caused by the presence of 
nitrates seems to disappear when the organic material is 
diluted to the considerable extent that exists in natural 
waters. The high chlorine found in some well-waters does 



108 AIR, WATER, AND FOOD. 

not interfere with the method to any extent, but this deter- 
mination does not possess much value in this class of waters, 
which are low in organic nitrogen. 

In carrying out the digestion with sulphuric acid, the 
greatest care must be taken to prevent access of ammonia or 
dust from any source. The acid solutions will absorb am- 
monia from the air or from the dust of the laboratory if they 
are allowed to remain uncovered for any length of time. 
This source of error may in some instances be sufficiently 
large to render a determination valueless, even in a room 
which is to all appearances free from ammonia-fumes. 
Hence the operation should, if possible, be carried to com- 
pletion within twenty-four hours, and for every set of deter- 
minations a blank analysis should be made with ammonia- 
free water in order to make a correction for the ammonia in 
the reagents, and for that accidentally introduced during the 
process. 

As the result of many hundred comparative determina- 
tions of the organic nitrogen and of the albuminoid ammo- 
nia in natural waters which take their origin in the glacial 
drift, it has been found that the nitrogen given by the albu- 
minoid-ammonia process as directed in the previous pages 
is about one-half of the total organic nitrogen as given by the 
Kjeldahl process; in the case of sewages and polluted waters 
it is very variable owing to their irregular composition. 

Determination of Nitrogen in the Form of Nitrites. 
— Directions. — When the determination of the free and 
albuminoid ammonia is well under way, the estimation of 
nitrogen in the next stage of decay, that of nitrites, should 
be begun. If the water is colorless, measure out the required 
amount, usually ioo c.c, into a ioo-c.c. tube. If the water 
possesses color which cannot be removed by simple filtra- 
tion, it should be decolorized as follows: Thoroughly rinse 



water: analytical methods. 109 

with the water a 250-c.c. glass-stoppered bottle; pour into 
it about 200 c.c. of the sample, add about 3 c.c. of the milk 
of alumina and shake the bottle vigorously. Let the bottle 
stand for ten or fifteen minutes and filter through a small 
plaited filter which has been thoroughly washed with water 
free from nitrites. From this filtrate take 10 c.c. for nitrates 
(see p. no). To 100 c.c. of the filtered sample or of the origi- 
nally colorless water add 10 c.c. of sulphanilic acid in acetic 
acid and 10 c.c. of naphthylamine acetate. 

After standing 5 to 10 minutes, not longer, compare with 
the standards made with the nitrite solution or, better, with 
2x4 inch pieces of Milton Bradley's standard papers* the VR, 
violet-red tint 2 which is an exact match for the color given 
by 5 c.c. or VR, tint 1, which matches 10 c.c. of the stand- 
ard nitrite solution in a ioo-c.c. Nessler tube with a depth 
of 5 inches to the graduation. If 100 c.c. of the sample is used 
this measures the nitrites in parts per million. Good waters 
show considerably less than .005, suspicious waters between 
.005 and .010, bad waters may show from .000 to .300 or even 
more. The same use of the foot rule and aliquot part may 
be made as above in the ammonia determination. 

One cubic centimeter of the standard nitrite solution contains 
0.0000001 gram N as nitrite. The determination must be 
completed within half an hour, since the air of a room in which 
gas is burned contains nitrites. f 

Notes.— If the color obtained is more . than . that given by 
20 c.c. of the standard solution, as it may. be in the case of 
water from bad wells and sewage effiuents,. the water should 
be diluted with nitrite-free water, 10 c.c. or even 1 c.c. being 
made up to 100 c.c. before adding the reagents, since colors 

* Mulliken's "Identification of Pure Organic Compounds,"' Sheet A, Color 
Standard. 

f Defren: Tech. Quart., g (1896), 238; Axson: loc. cit., 12 (1899), 219. 



IIO AIR, WATER, AND FOOD. 

above 20 c.c. are too deep for accurate comparison. In many- 
cases, however, it may be more convenient and sufficiently 
accurate, where the colors are not very much greater than 
20 c.c, to read the color in an aliquot part, as described in 
the determination of ammonia on page 104. 

The reactions which take place consist first in the diazotiz- 
Ing of the sulphanilic acid by the nitrite present in acid solu- 
tion, forming diazobenzenesulphonic anhydride. This reacs 
with the naphtylamine hydrochlorate, forming azo-or-amido- 
naphtylic parabenzol-sulphonic acid, which gives the pink 
color to the solution, the amount formed depending upon 
the amount of nitrite present. 

' N ■ N H 

I: J i 

H— C C— H H— C C C— H 

II I I II I 

H— C C— H H— C C C— H 

v/ \/\// 

c c c 

I I I 

SO3H NH a H 

Determination of Nitrogen in the Form of Nitrates.* 

— Directions. — Nitrogen in the fourth stage, that of nitrates, 
is next determined. In the case of ground-waters, or sewage 
effluents, measure 2 c.c. from the bottle with a capillary pipette, 
into a three-inch porcelain evaporating-dish; for surface- 
waters, always low in nitrates, take 10 c.c. from the portion 
already decolorized in the determination of the nitrites. Place 
the dishes on the top of the water-bath and let their contents 
evaporate gently until one or two drops are left; then set them 
away in a place free from dust, that the remainder may evapo- 
rate spontaneously. Do not let them go quite to dryness on 
the bath. 

* Sprengel: Pogg. Ann., 121, 188. Grandval and Lajoux: CompL rend. y 
101, 62. Gill: J. Am. Chent. Soc, 16 {1894), 122. 



water: analytical methods. hi 

When the water is entirely evaporated, drop six drops of 
phenol-disulphonic acid directly upon the dry residue and 
rub it around with a glass rod to insure complete contact of 
the acid and the residue in the dish. Dilute the acid with 
7 ex. of distilled water and add 3 c.c. of ammonium hydrate 
(1:1) or if only one laboratory is available KOH (1:3) since 
no ammonium hydrate solutions should be allowed in a distilling 
laboratory. 

To prepare the standards to be matched in the small porce- 
lain dishes, measure out the varying amounts of the standard 
nitrate solution, for instance 0.5, 1.0 c.c. to 8 c.c, add enough 
water to make the volume 10 c.c. and two or three drops of the 
alkaline hydrate. 

For very low or very high colors the matching is most 
satisfactorily done in 50-c.c. Nessler tubes, diluting to 50 c.c. 
or reading an aliquot portion. For matching the lowest colors, 
which in this case is safely done, 5 or 6 inch high tubes cut 
from broken Nessler tubes are very satisfactory. 

To prepare standards in Nessler tubes. A portion of water 
is made alkaline, and the standard is run in little by little until 
it matches the lowest color. Then more is added until the next 
color is matched, and so on to the highest color. 

Notes. — It will be found that if 10 c.c. of a colored water 
be evaporated directly, the color obtained with the reagents 
will be much deeper as well as browner than that given by 
the standards; hence the necessity for first decolorizing. 

Chlorides interfere with the accuracy of the method, but 
not to any extent when chlorine is present in less than 20 parts 
per million. If the amount of chlorine be more than this, the 
evaporation should be made in vacuo over sulphuric acid. 
Nitrites do not interfere with the test. 

The reaction is generally considered to consist in the 
formation of picric acid. While this is not quantitatively 
true, it offers the best explanation of the changes that occur. 



II 2 AIR, WATER, AMt> FOOD. 

Trinitrophenol (picric acid) is formed by the action of the 
nitrates in the cold, dry residue upon the phenol-disulphonic 
acid with which it is moistened: 

OH OH 

l A 

H— C C— SO,H NO,— C C— NO, 

|| | J- 3 HNO,= II | +2H,SO. 

H— C C— H H— C C— H 

\ // \ / + H,0 

C C 

I I 

SO.H NO, 

Phenol-disulphonic acid. Picric acid. 

The addition of an excess of caustic alkali converts the 
picric acid to the alkali picrate, which imparts an intense yel- 
low color to the liquid. The best color is obtained by the 
use of ammonia. 

Large quantities of nitrates in colorless water may be de- 
termined by reduction to ammonia by sodium amalgam, or 
by any reaction which yields nitrogen, this being measured as gas. 

Determination of the Carbonaceous Matter or " Oxy- 
gen Consumed." 

KubeVs Hot Acid Method. 

Reagents. — Ammonium oxalate 0.888 gram in one liter 
distilled water. One c.c. is equivalent to 0.0001 gram of 
oxygen. Potassium permanganate 0.4 gram in one liter dis- 
tilled water, standardize against the ammonium oxalate solution 
and make the necessary correction. If exact, 1 c.c. is equivalent 
to 0.0001 gram available oxygen. 

Directions. — Measure 100 c.c. of the water into a 250-c.c. 
flat-bottomed flask, add 10 c.c. of sulphuric acid (1:3) and 
about 10 c.c. of the potassium permanganate. Place the flask 
oh wife gauze and heat it quickly to boiling. Boil the solution 
for exactly two minutes; remove it from the flame; let it cool 
one minute, and add 10 c.c. of the ammonium oxalate. Titrate 



water: analytical method. 113 

with the permanganate to a faint permanent pink color. Each c.c. 
of the exact permanganate used in excess of the oxalate solution 
used represents 0.0001 gram of oxygen consummed by the sample. 

Notes. — For highly colored surface-waters 25 c.c. are 
taken and diluted to 100 c.c. with water free from organic 
matter; for sewages 10 c.c. are diluted in the same way. 

The oxygen given up by the permanganate combines 
with the carbon of the organic matter and perhaps to a cer- 
tain extent with the hydrogen, but not with the nitrogen. 
The amount of oxygen consumed bears some relation, there- 
fore, to the amount of organic carbon present in the water r 
but this relation certainly cannot be taken as a definite one 
in every case, the results varying even with the time of 
boiling. The method has its greatest value when it is 
used to compare waters of the same general character and 
having the same origin; for example, in making periodical 
tests of the purity of the effluent from a filter. Furthermore^ 
in order that the results shall have this comparative value, 
it is absolutely necessary that the process shall always be 
carried out in exactly the same way, even to the minutest 
detail of quantity, time, and temperature. 

In some cases it may be found advantageous to heat the 
solution upon the water-bath for half an hour instead of boil- 
ing it for five minutes. The results, however, will not be 
exactly comparable with those obtained by boiling. 

- Different kinds of organic matter behave differently with 
various oxidizing agents, so that a comparison of the results 
obtained with different oxidizing agents may throw light 
upon, the character of the organic matter, as well as i f s 
amount.* In waters from the watersheds of eastern Nor^h 
America the color and the oxygen consumed have a certain, 
though somewhat varying, relation, , I 

< Determination of Chlorine, r^The chlorine is deter- 
mined in natural waters by the method in general use; 

* Woodman: /. Am. Chem. Soc, 20 (rSgS), 497. 



114 AIR > WATER, AND FOOD. 

namely, titration with a solution of silver nitrate, using potas- 
sium chromate as an indicator. Since the exact change of 
color which constitutes the end-point will vary with the 
sensitiveness of the eyes of different observers to red, each 
person should standardize the silver nitrate solution for him- 
self. To do this, measure into a six-inch porcelain dish 25 
c.c. of distilled water; add 5 c.c. of sodium chloride solution 
(1 c.c. — 0.001 gram CI) from the burette and three drops of 
potassium chromate solution. Titrate with the silver nitrate 
solution until the yellow color of the liquid assumes the faint- 
est tinge of reddish brown. 

Directions. — Waters which are high in chlorine, i.e., which 
contain 20 or more parts per million, are titrated directly, 
using 25 c.c. either with or without the addition of 5 c.c. of 
the salt solution. Waters which are low in chlorine are con- 
centrated before titration, 250 c.c. being evaporated to 25 c.c. 
on the water-bath. Brown surface-waters should be decol- 
orized as follows: Pour into a 750-c.c. flat-bottomed flask 
about 500 c.c. of the water. Add 3 c.c. of the milk of 
alumina; shake and heat the water quickly to boiling on an 
iron plate. When the liquid comes to a full boil, at once 
remove the flask from the plate to avoid loss by evaporation. 
Place it in an inclined position to allow the alumina to settle. 
Decant off 250 c.c. of the colorless water into a six-inch dish 
for concentration to 25 c.c, using a flask calibrated for both 
the hot and the cold solution. Before making the titration, 
rub down the sides of the dish above the liquid with a small 
quantity of distilled water free from chlorine, using a clean 
feather. Rinsing alone will not always dissolve the chlo- 
rides which adhere to the sides of the dish. 

Notes. — For titration by this method the solution must 
be as nearly neutral as possible If the water is alkaline to 
.any extent, it should be neutralized with dilute sulphuric acid, 



water: analytical methods. 115 

using phenolphthalein as an indicator. The solution will 
then contain alkali only as bicarbonate, which does not 
interfere with the titration. Acid water must be made neu- 
tral by the addition of sodium carbonate. 

It is important that the process be carried out essentially 
as described, since it has been found that the results vary 
with the volume of solution in which the titration is made, 
the amount of chromate used, and the amount of precipitated 
silver chloride present.* A correction for volume can be 
made by means of the formula given by Hazen. 

E. G. Smith t recommends titration in a volume of 
100 c.c., making a correction of .1 c.c. more or less as found 
for the error due to dilution of the reagents. 

Color is removed by agitation with milk of alumina as 
before described. 

Determination of the Residue on Evaporation and 
the Loss on Ignition. — Directions. — Ignite and weigh a 
platinum dish. Measure into it 100 c.c. of the water (200 
c.c. in the case of surface-waters), and evaporate to dryness 
on the water-bath. When the water is all evaporated heat 
the dish in the oven at the temperature of boiling water for 
two hours, then let it remain in a desiccator over sulphuric 
acid for several hours and weigh.J The increase in weight 
gives the " total solids " or " residue on evaporation." If 
from a ground-water, save the residue for the determination 
of the iron. 

In the case of surface-waters the residue should be ignited 
and the loss on ignition noted. Heat the dish in a " radia- 
tor," which consists of another platinum dish enough larger 
to allow an air-space of about half an inch between the two 
dishes, the inner dish being supported by a triangle of plati- 
num wire. Over the inner dish is suspended a disk of 

* Hazen: Am. Chem. Jour., 11 (iSSg), 409. 

\ Trans. Wis. Acad. Sciences, Arts, and Letters, Vol. XIII, 359. 

Jin some laboratories it is the practice to dry at no° or 130 C. 



n6 



AIR, WATER, AND FOOD. 



platinum-foil to radiate back the heat into the dish. The 
larger platinum dish is heated to bright redness by a triple 
gas-burner. Heat the dish in the radiator until the residue is 
white or nearly so. Note any blackening or charring of the 
residue and any peculiar " burnt odor " which may be given 
off. After the dish has cooled, slightly moisten the residue 
with a few drops of distilled water to secure weighing under 
the same conditions. Heat the residue in the oven for half an 
hour; cool in a desiccator and weigh. This gives the weight 
of " fixed solids," the difference being the " loss on ignition." 

Notes. — Before the introduction of modern methods of 
water-analysis the determination of " loss on ignition " was 
the only method for the estimation of organic matter in 
water. In order, however, that the determination shall pos- 
sess any real value, it is necessary to regulate carefully the heat 
during the ignition, so as to destroy the organic matter with- 
out decomposing calcium carbonate or volatilizing the alkali 
chlorides. 

This is what the use of the radiator is intended to accom- 
plish, and in the case of surface-waters, with low mineral con- 
tent and considerable organic matter, the method gives gen- 
erally satisfactory results. But in the case of ground-waters 
having little or no organic matter and high mineral content 
the loss is often very great on account of the decomposition 
of nitrates and chlorides of the alkaline earths and the loss of 
water of crystallization. In waters of this class the determi- 
nation of " loss on ignition " is, therefore, generally meaning- 
less, although an approximation to the amount of organic 
matter can be obtained by the addition of sodium carbonate to 
the water before evaporating to dryness. By this means the 
alkaline earths are precipitated as carbonates, the chlorine 
and nitric acid are held by an alkaline base, and there is no 
water of crystallization in the residue. Even with this modi- 
fication the loss is considerable when magnesium salts are 
present, owing to the loss of carbonic acid. ,0 - r; 



water: analytical methods. 



117 



The behavior on ignition is oftentimes significant. 
Swampy or peaty waters give a brownish residue on evapora- 
tion to dryness, which blackens or chars, and this black sub- 
stance burns off quite slowly. The odor of the charring is 
like that of charring wood or grain; sometimes sweetish, but 
not at all offensive. Waters much polluted by sewage blacken 
slightly; the black particles burn off quickly and the odor is 
disagreeable. Any observations on this point should be re- 
corded in the report (p. 141 ) under the heading " Change on 
Ignition." 

Determination of the Hardness. 

1. By Soap. — Clark's Method. 

Directions. — Measure 50 c.c. of water into a 200-c.c. clear 
glass-stoppered bottle and add the soap solution from the 
burette, two or three tenths of a cubic centimeter at a time, 
shaking well after each addition, until a lather is obtained 
which covers the entire surface of the liquid with the bottle 
lying on its side, and is permanent for five minutes. The 
number of parts of calcium carbonate corresponding to the 
volume of soap solution used is found in the table in Appen- 
dix A. 

This will give the total hardness. If it is desired to find 
the permanent hardness also, dilute 50 c.c. of the water to 
about 200 c.c. and boil down to 50 c.c. in a beaker, cool and 
determine the hardness as before. This will give the per- 
manent hardness, and the difference will be the temporary 
hardness. 

Notes. — When potassium or sodium soap is added to 
water containing calcium and magnesium salts, the soap is 
decomposed, and insoluble compounds with the fatty acids 
are formed. The importance of adding the soap in small quan- 
tities cannot be too strongly emphasized, especially in the 
presence of magnesium compounds. The presence of mag- 



Il8 AIR, WATER, AND FOOD. 

nesium salts will be recognized by the peculiar curdy appear- 
ance of the precipitate formed and by the occurrence of a 
false end-point, the lather lasting about three minutes when 
the titration is about half done. If much carbonic acid be 
'liberated, it is better to follow Dr. Clark's original directions 
and remove it by suction. 

By reference to the table it will be observed that values 
are not given fcr more than 16 c.c. of the soap solution. If 
in any case the water under examination requires more than 
10 c.c. of the standard soap solution, a smaller portion of 
25 c.c, 10 c.c. or even 2 c.c, as the case may require, is meas- 
ured out and made up to a volume of 50 c.c with recently 
distilled water. If the volume of soap used is always about 
7 c.c, this will keep the results comparable with each other, 
although the element of dilution introduces an error. Potable 
waters, in the eastern United States, at least, are rarely so 
high in mineral matter as to require excessive dilution. In 
the case of extremely hard waters, however, the acid 
method is to be preferred. Distilled water itself, containing 
no calcium salt whatever, requires the use of a considerable 
quantity of soap to produce a permanent lather. The cause 
for this seems to exist in the dissociation of the greater part 
of the soap at the extreme dilution to which it is subjected,, 
and the slow accumulation of a sufficient quantity of undis- 
sociated soap to allow of the increase of surface tension to a 
point at which soap-bubbles will persist. 

By the temporary hardness of water is meant the hardness 
which is removed by boiling. It is due to the carbonates of 
calcium and magnesium held in solution by the carbonic acid 
in the water, probably in the form of bicarbonates. Perma- 
nent hardness is that which is not removed by boiling. It is. 
caused by the presence of soluble salts of calcium and mag- 
nesium, not carbonates, but chlorides and sulphates princi- 
pally, held in solution by the solvent power of the water itself.. 



WATER: ANALYTICAL METHOD. II9 



2. By Acid. — Hehner's Method* 

ALKALINITY. 

Directions. — For the determination of the " alkalinity," 

measure ioo c.c. of the water into a clear bottle such, as is used 

for the soap test, and add 2.5 c.c. of the erythrosine indicator, 

0.1 gram of the sodium salt in 1 liter of distilled water, and 

5 c.c. of chloroform neutral to erythrosine. Mix well by shaking 

N . 

and add — sulphuric acid from the burette in small quantities, 

shaking thoroughly after each addition. The pink color grad- 
ually grows lighter until the addition of a drop or two of the 
acid causes it to disappear entirely. Each tenth of a cubic 
centimeter of acid used represents one part of CaC0 3 in 1,000,000. 
Make a correction for the indicator by carrying out a blank 
determination with distilled water. 

The alkalinity may be determined more quickly as follows. 
Measure 100 c.c. of the water to be tested into a No. 6 evapo- 
rating dish, add two drops of sensitive methyl orange and titrate 

with the — sulphuric acid. Lacmoid and phenacetolin can 

also be used in the determination of the alkalinity, but they 
necessitate titration in a hot solution on account of their sus- 
ceptibility to carbonic acid. 

■Notes.— This method is especially useful for waters which 
require clarification by alumina and subsequent filtration. 

i The use of chloroform is essential to secure a sharp end- 
point. The non-ionized erythrosine formed by the addition 
of the acid to its alkali salt is soluble in the aqueous solu- 



* Hehner: Analyst, 1883, 8, 77; Draper, Chem. News, 1885, 51, 206: Ellms: 
Jour. Am. Chem. Soc, 1899, 21, 239. 



120 AIR, WATER, AND FOOD. 

tion with a slight rose color. It is, however, more soluble 
in the chloroform, and when it is thus removed as fast as 
formed the neutralization of the alkali becomes at once 
apparent.* 

If a water contains sodium or potassium carbonate, 
there will not be any permanent hardness, and hence more 
acid will be required for the filtrate than corresponds to the 
amount of sodium carbonate added. From the excess 
the amount of sodium carbonate in the water may be 
determined. Any alkali carbonate present would be 
calculated as temporary hardness by the direct titration; 
hence it should be calculated to calcium carbonate and 
subtracted from the results found by the direct titra- 
tion. 

Determination of Phosphates. f — Directions. — Evapo- 
rate 50 c.c. of the water and 3 c.c. of nitric acid (sp. gr. 1.07) 
to drvness in a 3 -inch porcelain dish on the water-bath. 
Heat the residue in an oven for two hours at the tempera- 
ture of boiling water. Treat the dry residue with 50 c.c. 
of cold distilled water, added in several portions and poured 
into the comparison-tube. It is not necessary to filter the 
solution. Add 4 c.c. of ammonium molybdate (50 grams 
per liter) and 2 c.c. of nitric acid, mix the contents of the 
tube and compare the color, after three minutes, with stand- 
ards made by diluting varying quantities of the standard 
phosphate solution (1 c.c. =0.0001 gram P 2 5 ) to 50 c.c. with 
distilled water and adding the reagents as above. Carry 
out a blank determination on the distilled water used for 
dilution, especially if it has stood for any length of time in 
glass vessels. 



* Ellms: /. Am. Chetn Soc, 21 (i8qq), 359. 

fLepierre- Bull. Soc. Chim., 15 (1896), 1213 Woodman and Cayvan: 
J. Am. Chem. Soc, 23 (iqoi), 96. Woodman- ibid. (1902), 735. 



WATER: ANALYTICAL METHODS. 12 1 

Notes. — The method as described will be sufficient for 
ordinary work. If a more exact determination of the phos- 
phate is required, a slight correction should be made in each 
case. For a table showing these corrections reference may 
be made to the paper by Woodman and Cayvan previously 
cited. 

The evaporation and heating w T ith nitric acid is for the 
purpose of removing silica, which gives with ammonium 
molybdates a yellow color similar to that given by phos- 
phates. 

The determination of phosphates in a drinking-water is 
a matter which has not received the attention from water 
analysts that has been given to the estimation of various 
other constituents. Any one who looks through the litera- 
ture cannot help noticing how few are the published 
results of quantitative estimations of the phosphate con- 
tent of natural waters, apart from mineral waters. Yet 
this determination, by reason of the conversion of 
organic phosphorus compounds into phosphates through 
the processes of decay, is one which might reasonably 
be expected to throw considerable light on the question 
of the pollution of natural waters by objectionable ma- 
terial. 

The reasons for this dearth of published data are not 
far to seek. To be of value the amount of phosphate must 
be known within rather narrow r limits. Qualitative tests 
are not sufficient. The mere presence of phosphates is by 
no means definite or even confirmatory evidence of organic 
pollution. Rocks and minerals containing phosphates are 
found nearly everywhere, and traces, at times even con- 
siderable quantities, may be dissolved, especially by waters 
rich in carbonic acid. This, however, does not constitute 



122 AIR, WATER, AND FOOD. 

a serious objection to the utility of the determination. The 
same is true of many if not most of the constituents upon 
which reliance is placed in judging of the quality of a water. 
Unpolluted waters often contain notable amounts of nitrates 
and chlorides, and a true judgment can be rendered only 
after comparison with samples from adjacent but unpol- 
luted sources. 

The chief reason, however, has been the lack of an accu- 
rate and simple method, sufficiently delicate, and of enough 
data to work out a standard for comparison. 

This reason can hardly hold true now, for enough work 
has been done on the colorimetric method to indicate its 
value as another link (of which we have none too many, any- 
way) in the chain of circumstantial evidence by which we 
are often compelled to judge the purity of a water. 

The amount of phosphate and its variation seem to fol- 
low the same general line as the other mineral constitu- 
ents which either accompany the polluting material or are 
produced by its decay, especially the nitrates and chlorides. 
It is not, however, so delicate an indicator as these. In 
general it may be said that the amount (expressed as P 2 5 ) 
in an unpolluted water will seldom be over i.o part per 
million. 

Determination of Iron.* — Directions. — Evaporate iooor 
200 c.c. of the water to dryness in a platinum dish. (The 
weighed residue from the determination of total solids may 
be used if desired.) Treat the residue with 5 c.c. of hydro- 
chloric acid (1:1), being careful to carry the acid to the edge 
of the dish. In some cases it may be necessary to heat the 
dish gently on the water-bath in order to bring all the iron 

* Thomson: J. Chem. Soc, 67 (1885), 493. 



WATER: ANALYTICAL METHODS. 123 

into solution. When all is dissolved with the exception of 
silica, rinse the solution into a ioo-c.c. tube and make it up 
to about 50 c.c. with distilled water. Add a solution of po- 
tassium permanganate drop by drop until the solution re- 
mains pink for 10 minutes. 

Meanwhile prepare a blank standard with 5.0 c.c. of dis- 
tilled water and about a cubic centimeter of hydrochloric 
acid. Add 15 c.c. of potassium sulphocyanide solution to 
the waters and to the blank standard. Add the standard 
iron solution, in small quantities, .02 c.c. if necessary, from 
a capillary pipette, mixing thoroughly by pouring the solu- 
tion back and forth from one tube to another after each 
addition, until the color of the standard matches that of 
the water. One cubic centimeter of the standard iron solu- 
tion is equal to 0.000 1 gram of Fe. 

Notes. — In the case of some river-waters it will be fpund 
necessary to add a few cubic centimeters of hydrochloric 
acid to the water while evaporating, in order to facilitate 
the solution of the iron. This should be done on a separate 
portion from that used for the determination of total 
solids. 

The colors should be matched immediately after adding 
the sulphocyanide, since the color fades appreciably on 
standing. The highest standard should not contain more 
than 3 c.c. of the iron solution, since the color then becomes 
too deep for accurate comparison. 

Determination of the Dissolved Oxygen. 

Method of L. W. Winkler* 

Collection of Samples. — The samples are collected in 
glass-stoppered bottles of known capacity, holding about 



* Berichte, 21 (1888), 2843. 



124 AIR » WATER, AND FOOD. 

250 cubic centimeters. When water is taken from a faucet 
the bottle is filled by means of a tube which passes to the 
bottom of the bottle. A considerable amount of water is 
allowed to pass through the bottle and overflow at the top. 
It will be almost impossible to obtain duplicate samples 
unless the bottles are filled at the same time by means 
of a T tube, owing to variations in pressure in the 
pipes. 

In taking samples from a stream or pond, a stopper 
with two holes is used. A tube passing through one of 
these holes is sunk in the water to the desired depth, and 
the other is connected with a larger bottle of at least four 
times the capacity of the smaller one, and fitted in the same 
way. From the larger bottle the air is exhausted by the 
lungs or by an air-pump until it is nearly filled with water. 
Unless the determination is to be made at once, the rubber 
stopper of the smaller bottle is quickly replaced by the 
glass stopper so that no air is left in the bottle. The 
temperature of the water at the time of sampling should 
be noted. 

The apparatus which has been used in connection with 
work in this laboratory for collecting samples at various 
depths down to 75 feet is shown in outline in Fig. 11. A gal- 
vanized-iron can of such size as to hold one of the gallon bot- 
tles is weighted with lead and provided with ears at the top 
for suspending. The bottle, which is securely wired in, is pro- 
vided with a rubber stopper carrying two brass tubes, one 
ending just below the stopper and projecting for about 8 or 
9 inches above it, the other extending to the bottom of the 
bottle and connected by heavy rubber tubing with the 
sample bottle. This is held by brass brackets, which are 
fastened by means of a wooden cleat to the side of the can. 
The neck of the bottle is put into the slot in the .upper 



WATER: ANALYTICAL METHODS. 



125 



bracket and then it is firmly clamped by the thumb-screw 
of the lower one. The arrangement of tubes in the sample 
bottle is obvious. In using the apparatus it is quickly 




Fig. 



lowered to the desired depth by means of a rope marked off 
in feet. The water enters the sample bottle and flows 
through it into the other. When the bubbles cease to rise, 
indicating that the larger bottle is full, thus replacing the 
water in the sample bottle a number of times, the apparatus 
is drawn to the surface. The temperature is read from a 
thermometer fastened to the tube inside the gallon bottle. 
The Determination. — Remove the stopper and add 2 c.c. 
of manganous sulphate solution with a pipette having a 
long capillary point reaching to the bottom of the bottle, 
and in the same way add 2 c.c. of the solution of sodium 
hydroxide and potassium iodide. Insert the glass stopper, 
leaving no bubbles of air, and mix the contents of the bottle. 



126 AIR, WATER, AND FOOD. 

f 

Allow the precipitate to settle, and add 3 c.c. of strong 
hydrochloric acid with another pipette ; add also one or two 
small glass beads and again insert the stopper. When the 
white portion of the precipitate is entirely dissolved, pour 
out a part of the solution into a flask, put back the stopper 
and shake the bottle vigorously. Then rinse out the con- 
tents of the bottle into the flask and titrate the liberated 

N 
iodine with approximately — sodium thiosulphate until the 

color becomes a faint yellow. Then add starch solution 
and titrate to the disappearance of the blue color. The 
first end-point should be taken, as the color will return on 
account of the reducing action of the organic matter present. 

OXYGEN DISSOLVED. 

From Report on Standard Methods. 

Sulphuric Acid. — Specific gravity 1.4 (dilution 1:1). 

Sodium Thiosulphate Solution. — Dissolve 6.2 grams of 

chemically pure recrystallized sodium thiosulphate in one 

N - 
liter of distilled water. This gives an — solution, each c.c. 

40 

pf which is equivalent to .0002 gram of oxygen or .1395 c - c - 

of oxygen at o° C. and 760 mm. pressure. Inasmuch as 

.this solution is not permanent, it should be standardized 

N 
"occasionally against an — solution of potassium bichromate 

as described in almost any work on volumetric analysis. 
The keeping qualities of the thiosulphate solution are im- 
proved by adding to each liter 5 c.c. of chloroform and 1.5 
grams of ammonium carbonate before making up to the 
prescribed volume. . 
r "Calculation of Results.— The standard method of ex- 



water: analytical methods. 127 

pressing results shall be by parts per million of oxygen by 
weight. 

"It is sometimes convenient to know the number of c.c. 
of the gas per liter of o° C. temperature and 760 mm. pres- 
sure, and also to know the percentage which the amount of 
gas present is of the maximum amount capable of being 
dissolved by distilled water at the same temperature and 
pressure. All three methods of calculation are therefore 
here given: 

Oxygen in parts per million 





0.0002N X 1 


.000,000 200N 




V 




~ V 


in c.c. 


per liter 








0.1395NX: 


[OOO 


i39-5 N 




V 




V 



Oxygen in per cent, of saturation 

200N X 100 2o,oooN 

= vxo = "~vo 

N 
Where N = number of c.c. of — thiosulphate solution, 

V = capacity of the bottle in c.c. less the vol- 
ume of the manganous sulphate and potas- 
sium iodide solution added (i. e., less four 
c.c). 

= the amount of oxygen in parts per million in 
water saturated at the same temperature and 
pressure." 



128 



AIR, WATER, AND FOOD. 



QUANTITIES OF DISSOLVED OXYGEN IN PARTS PER MILLION BY 
WEIGHT IN WATER SATURATED WITH AIR AT THE TEMPERATURE 
GIVEN. 



Temp. C. 


Oxygen. 


Temp. C. 


Oxygen. 


Temp. C. 


Oxygen. 


Temp. C. 


Oxygen. 


o 


14.70 


8 


11.86 


16 


9-94 


24 


8.51 


I 


14-28 


9 


11.58 


17 


9-75 


2 5 


8-35 


2 


13.88 


10 


II. 31 


18 


9.56 


26 


8.19 


3 


I3-50 


11 


11 05 


19 


9 37 


27 


8.03 


4 


13 14 


12 


10.80 


20 


9.19 


28 


7.88 


5 


12.80 


13 


IO-57 


21 


9 01 


29 


7-74 


6 


12.47 


14 


IO-35 


22 


8.84 


30 


7.60 


7 


I2.l6 


15 


IO.14 


2 3 


8.67 







Notes. — This determination is a good illustration of an 
indirect volumetric process. A precipitate of manganous 
hydroxide is formed in the bottle by the reaction of the 
manganous sulphate and the sodium hydroxide. This imme- 
diately combines with the oxygen in the water to form a cer- 
tain amount of manganic hydroxide. The hydrochloric acid 
which is added reacts with the manganic hydroxide to form 
chlorine, which in turn liberates iodine from the potassium 
iodide, the amount thus set free depending primarily upon 
the quantity of oxygen dissolved in the water. The presence 
of considerable amounts of organic matter or of nitrites in- 
troduces an error. In such cases the method must be modified 
or a correction made. Details of the method used in such 
cases are given in the paper by Winkler previously cited. 

A correction is made for the volume of the reagents 
added, but since the precipitated hydroxides had settled 
before the acid was added, no allowance should be made for 
the amount of acid, since the water it displaces contains 
neither oxygen nor iodine. 



water: analytical methods. 12 o> 

is a constant for any particular bottle, and its logarithm 
may be recorded in a note-book or upon the bottle itself. 

If water is collected in the ordinary way and transferred. 
to the apparatus by pouring, there will inevitably be an ab- 
sorption of oxygen unless the water is already saturated. 
Thus a process which gives excellent results when the water 
is nearly or quite saturated may fail entirely to give accurate 
results when the dissolved oxygen is low or absent. The 
water may be supersaturated with oxygen, in which case the 
per cent, of saturation may be more than one hundred.* 

Determinations of dissolved oxygen in ponds and 
streams are best made on the spot, or at least the re- 
agents should be added. The very simple apparatus re- 
quired for the Winkler process can be packed in small space, 
and the entire determination requires only a few minutes. 
The absorption of the oxygen by the manganous hydroxide- 
is complete almost at once, and it is unnecessary to allow it 
to settle for a long time before adding the acid. The titra- 
tion can be made with a small burette or pipette with accurate 
results. 

Determination of Free Carbonic Acid. — Reagent. — Stand- 

N 
ard — solution of sodium carbonate. Dissolve 2.41 grams of 

dry sodium carbonate in one liter of distilled water which has 
been freed from carbonic acid by cautious addition of dilute 
solution of sodium carbonate. Add 5 c.c. of phenolphthalein 
indicator (7 grams in a liter) to the distilled water before 
neutralizing and measuring. Preserve this solution in bottles 
of resistant glass, protected from the air by tubes filled with- 
soda lime. One c.c. equals 0.001 gram of C0 2 . 

♦Gill: Tech. Quart., 5 (1892), 250. 



130 AIR, WATER, AND FOOD. 

Procedure. — Measure 100 c.c. of the sample into a tall, 

narrow vessel, preferably a 100 c.c. Nessler tube, and titrate 

N 
rapidly with the — sodium carbonate solution, stirring gently 

until a faint but permanent pink color is produced. 

N 
The number of c.c. of — sodium carbonate solution used in 
22 

titrating 100 c.c. of water, multiplied by 10, gives the parts per 

million of free carbonic acid as C0 2 . 

Owing to the ease with which free carbonic acid escapes 
irom water, particularly when present in considerable quanti- 
ties, it is highly desirable that a special sample should be 
collected for this determination, which should preferably be 
made on the ground. If the analysis cannot be made on the 
spot, approximate results from water not high in free carbonic 
acid may be obtained from samples collected in bottles which 
are completely filled so as to leave no air space under the 
stopper. 

Notes. — The reaction consists in the formation of acid 
sodium carbonate: 

Na 2 C0 3 + H 2 4-CO2 = 2NaHC0 3 . 

The acid carbonate does not give a pink color with phenol- 
phthalein. 

Determination of the Color. — The amount of color is 
generally determined by direct comparison of the water with 
some definite standard of color. Various standards of color 
have been proposed, the objection to most of them being 
that they are not sufficiently general in their application, 
Being adapted only for the color of some particular class of 
waters. 



water: analytical methods. 131 

Nesslerized Ammonia Standards .—The yellowish-brown 
"tint of the surface-waters of the Atlantic watershed corre- 
sponds, except in the lowest grades, very closely to that of 
nesslerized ammonia, so that the standards for reading 
ammonia can be used also for the determination of the 
color. The comparison is made in the same kind of 50-c.c. 
tubes that are used for the ammonia determinations, but 
the tubes used for this purpose are kept separate from those 
used for the ammonia, since the least amount of alkali re- 
maining in a tube (from imperfect washing, for instance) 
■alters the color of the water. The scale used corresponds 
quite closely with the amount of the standard ammonium 
chloride solution in the standards. Thus a color of 1.0 is 
nearly the same as that produced by the nesslerization of 1 
c.c. of the standard ammonia; c.i is about the color pro- 
duced with 0.1 c.c. of the ammonia solution. In the higher 
grades of color, above 1.0 or 2.0, the tint varies considerably 
from that of the nesslerized ammonia, and the degree of 
color is then better determined in wider tubes and in less 
depth. 

The degree of correspondence of the ammonia standards 
with the natural waters is dependent largely upon the sensi- 
tiveness of the Nessler's reagent, a solution which is so sen- 
sitive as to precipitate in two hours, matching the colors 
more closely than one which will remain for twenty- four 
hours. This is perhaps due to the reddish tinge given to the 
solution by the incipient precipitation of the mercuric 
iodide. 

Natural Water Standards. — To avoid these variations in 
•color, standards made from dark-colored water from swamps 
by various degrees of dilution, and verified by direct com- 
parison with suitably prepared nesslerized ammonia stand- 



132 AIR, WATER, AND FOOD. 

ards, are used. They have the same hue as the waters to be 
matched, as well as a degree of turbidity which corresponds 
well with that of surface-waters ; once prepared, they will 
keep for a fairly long time if protected from the light and 
from the dust. These are the standards that are in use in 
this laboratory. They are periodically standardized by 
comparison with the permanent glasses of a Lovibond 
Tintometer. 

Platinum Standards. — For ground-waters which have 
only very little color and considerable hardness, and for fil- 
tered waters, the platinum color standards are convenient.*" 
According to this scale, the color of a water is the amount of 
platinum in parts per ten thousand, which, together with 
enough cobalt to match the tint, must be dissolved to pro- 
duce an equal color in distilled water. In practice, a stand- 
ard having a color of 5.00 is prepared by dissolving 1.246' 
grams of potassium platinic chloride (equivalent to .5 gram 
platinum), 1.000 gram of cobalt chloride (equivalent to .25 
gram cobalt), and 100 c.c. of strong hydrochloric acid in dis- 
tilled water and diluting to one liter. 

Dilute standards for use are made by diluting varying 
amounts of this standard to 50 c.c. with distilled water. Thus, 
by diluting 1 c.c, 2 c.c, and 3 c.c. to 50 c.c, colors of 0.1, 0.2, 
and 0.3 are obtained. It is claimed that the platinum stand- 
ards are permanent if protected from the dust. 

Iodine Standards. — A standard for color which could be 
made up at the moment when wanted and without the use of 
costly apparatus would be a desideratum. Experiments made 
in this laboratory indicate that an aqueous solution containing 
a definite weight of iodine offers the best solution of the prob- 
lem. Owing, however, to the volatility of iodine even in 
dilute aqueous solution it is better to liberate it directly in 

* Hazen : Am. Chem. /., 14 (1892), 300. 



water: analytical methods. 133 

the comparison-tube itself. For this the following solutions 
are required: Potassium iodide, 0.1 gram per liter; potas- 
sium bichromate, 0.09 gram per liter; picric acid, 0.2 gram 
per liter. 

For a color of 5.0, 50 c.c. each of the iodide and of the 
bichromate solutions are used; for lower colors proportional 
amounts are taken and diluted to 100 c.c. with distilled water. 
To each tube is added 1 c.c. of the picric acid solution, and 
just before the colors are to be matched add 2 c.c. of strong 
sulphuric acid. The color develops, as in the case of nessler- 
ized ammonia, within ten minutes and can be relied upon 
for about half an hour. A very slight milkiness aids in match- 
ing the color; a great hindrance to the use of metallic solu- 
tions being their clearness or brightness as compared with 
natural waters. 

The comparison-tubes which give the most satisfactory 
results with colors from 5.0 to 0.5 on the natural water scale 
are 15 / 16 inch wide and 9V4 inches high to the 100-c.c. mark, 
For lower colors, narrower tubes, n /i6 mcn diameter and the 
same depth, give closer readings. 

Determination of the Odor. — Cold. — Shake violently 
the sample in one of the large collecting-bottles when it is 
about half or two-thirds full, then remove the stopper and 
quickly put the nose to the mouth of the bottle. Note the 
character and degree of intensity of the odor, if any. An 
odor can often be detected in this way which would be en- 
tirely inappreciable if the water were poured into a tumbler. 

Hot. — Pour into a beaker about five inches high enough 
water to one-third fill it. Cover the beaker with a well-fitting 
watch-glass and place it on an iron plate which has been pre- 
viously heated, so that the water shall quickly come to a boil. 
When the air-bubbles have all been driven off and the water 
is about to boil, take the beaker from the plate and allow it 
to cool for about five minutes. Then shake it with a rotary 



134 AIR, WATER, AND FOOD. 

movement, slip the watch-glass to one side and put the nose 
into the beaker. Note the odor as before. The odor may or 
may not be the same as that of the water when cold; it can 
be perceived, as a rule, for only an instant. 

Notes. — It is inevitable that a certain personal equation 
should influence this test. Each laboratory will have its own 
.standards for routine work, but a certain familiarity with the 
more common odors will tend to allay public anxiety and to 
aid in a more watchful habit on the part of consumers. Good 
ground-waters do not give distinct odors unless they are de- 
rived from clayey soil, but the odor often betrays a contami- 
nated wei! more surely than any other test. Surface-waters 
will nearly always yield a characteristic odor. This odor may 
be due to the organic matter contained in the water, or to 
the presence of minute plants or animal organisms. 

Among the odors which are frequently met are the 
" earthy," " vegetable," " musty," " mouldy," " disagree- 
able," and " offensive." The " earthy " odor is that of 
freshly turned clayey soil. u Vegetable " is the odor of 
many normal colored surface-waters; it may be described 
as swampy or marshy, pond-like, and is often strengthened 
by heating. " Musty " can be likened to the odor of damp 
straw from stables; it is fairly characteristic of sewage con- 
tamination, and by the trained observer is distinctly distin- 
guishable from the mouldy odor. " Mouldy " is the odor of 
upturned garden or forest mould, or of a moist hot-house; 
it is somewhat allied to the earthy odor. " Disagreeable " 
is a term which is capable of wide variation among different 
observers. It may include certain characteristic odors which 
are peculiar to the growth or decay of certain organisms, as 
the " pigpen " odor of Anabcena, the " fishy " or " cucum- 
ber " odor of Synura, etc. The term " offensive " is generally 
reserved for the sewages. These terms can be taken only as 
broad illustrations of the character of the particular odor, 



WATER ANALYTICAL METHODS. 13$ 

since the odor will very likely be described by different per- 
sons in different ways, and each laboratory will have its own 
characterization. The odor which often accompanies an 
abundant development of diatoms is a good illustration of 
this. It will be called by various inexperienced observers 
offensive, rotten, fishy, geranium-like, aromatic, in one and 
the same sample of water. 

The terms generally used to signify the degree of inten- 
sity of the odor are " very faint," " faint," " distinct," and 
" decided." The exact value to be placed on each of these 
terms will, as a matter of course, vary with the individual 
analyst, but in a general way it may be said that the " very 
faint " odor is one that would not be detected except by the 
trained observer; the " faint " odor would be recognized by 
the ordinary consumer if his attention were called to it; the 
" distinct " odor is one that would be readily noticed by the 
average consumer, but would not interfere with the use of 
the water; while the " decided " odor is one which would, in 
all probability, render the use of the water unpleasant. 

Biological Examination — The close relation of the odor 
to the living fauna and flora of the water makes it desirable 
that the chemist shall be able to recognize the more common 
forms of water plants and animals even if he makes no pre- 
tensions to a knowledge of cryptogamic botany or of zo- 
ology. Therefore a microscope and a concentration appara- 
tus should be in every water-laboratory. A full description 
will be found in Whipple.* 

The bacteriological examination belongs to the expert 
rather than to the student, certainly in the present state of 
our knowledge of the lower organisms. It may be desirable 
for the student to be familiar with the simpler methods of 
plate and tube culture, and the water-works laboratory 
should, as in the above case, be provided with means for plain 

* " Microscopy of Drinking-water." 2d ed. N. Y., Wiley. 



H36 AIR, WATER; AND FOOD. 

number counts, and directions for avoiding errors due to 
variations in temperature, time of culture, etc., consult 
Frankland's "Micro-organisms in Water"; "Manual of 
Bacteriology," Muir and Ritchie; "Water Bacteriology," 
Prescott and Winslow. 

Determination of the Turbidity and Sediment — The 
suspended matter remaining in the water after it has rested 
quietly in the collecting-bottle for twelve hours, or more, is 
called its turbidity, and that which has settled to the bottom 
of the bottle, its sediment. 

Good ground-waters are often entirely free from turbidity 
and sediment, the suspended matters having been filtered out 
during the subterranean passage of the water, but this is 
rarely true of surface-waters. The turbidity is various in 
character and amount, sometimes milky from clay or ferrous 
iron in solution; usually it consists of fine particles, generally 
living algae or infusoria. These often collect on the side 
toward or from the light, and a practised eye can, not infre- 
quently, recognize their forms. Some of the lower animal 
forms can also be seen by the naked eye, and the larger En- 
tomostraca are quite noticeable in many waters. 

The sediment may be earthy or flocculent; in ttie latter 
case it is generally debris of organic matter of various kinds. 
The degree of turbidity is expressed by the terms " very 
slight," " slight," " distinct," and " decided," and the degree 
of sediment by " very slight," " slight," " considerable," and 
" heavy." These determinations, again, are of value only to 
the routine worker, and for him there are various methods in 
use. The papers of Parmelee and Ellms * and of Whipple 
and Jackson f should be consulted for a description of these. 

Permanent standards, however desirable for a routine 
laboratory where many samples are tested daily, are not 
very reliable for students' work where the tests are made 

* Tech Quart., 12 {1899), 145. \Ibid. t 283. 



waier: analytical methods. 137 

only at intervals and for educational rather than technical 
purposes. 

Determination of Alum. — On account of the use of alum 
or aluminum sulphate as a coagulant in the filtration of 
water, a determination of alumina in the effluent water is 
often necessary. This may be readily made by the log- 
wood test.* 

Directions. — The logwood solution is made as follows: 
Take two grams of logwood chips and boil one minute in a 
platinum dish with 50 c.c. of distilled water. Decant the 
solution and boil again for one minute with 50 c.c. of water. 
Decant this and similarly boil a third time with 50 c.c. of 
water. Decant this into a platinum receptacle for use. 
Take three drops for each test. Kept in platinum, the solu- 
tion will last for several days at least. 

Test the water as follows: Boil 50 c.c. of the water in 
a platinum dish for a short time to expel carbon dioxide. 
Add three drops of the logwood solution and continue boiling 
for a few seconds to develop the color. Decant into a glass 
flask and cool quickly under the tap (so as not to keep the 
hot solution too long in the glass). Transfer to a No. 2 
beaker and blow in carbon dioxide from the breath by means 
of a glass tube until there is no further decolorization. Pour 
the water into a Nessler tube for comparison with standards 
similarly prepared. Allow them to stand several hours 
before taking the final reading. No wash-water is used at 
any of the decantations. The test shows one part of 
aluminum sulphate in 8,000,000 parts of water. 

A blank made with distilled water, if not completely 
decolorized by the C0 2 , will show a tint perceptibly fainter 



* E. H. Richards: Tech. Quart., 4 (1891), 194. A. H. Low, Tech. Quart., 
15 (1902), 351. 



1 3$ AIR, WATER, AND FOOD. 

than that produced by one part in 8,000,000 of aluminum 
sulphate. 

It should be noted that carbon dioxide must be kept 
absent until the point prescribed. The solution is therefore 
transferred to a beaker in order to keep the flask free from 
carbon dioxide for the next test. 

The main points are: 

1. Any kind of logwood appears to answer. 

2. The solution is good for several days, at least, if kept 
in platinum. 

3. The use of platinum instead of glass for boiling the test, 

4. The use of carbon dioxide instead of acetic acid. 
Aluminum hydrate, as pointed out by the late Professor 

A. R. Leeds in 1893, will produce a tint almost as strong as 
if it were in solution, but of a distinctly differing tint. 

Mr. Low's method of procedure is as follows: First, 
test the water as above described. If no tint, or none ex- 
ceeding that of the blank, remains after standing several 
hours or over night, that is sufficient. If, however, a tint 
persists, or a colored precipitate settles out, it is necessary 
to determine if this is due to aluminum hydrate. Pour a 
sample of the water several times through a double Swedish 
filter, and finally test the filtrate. If the tint produced is 
weaker than that given by the unfiltered water, repeat the 
operation on a fresh portion of the water, using the same 
filter, and continue repeating with new portions of the 
water and always using the same filter, until it is apparent 
that no further diminution of the tint can be effected. 

For a less delicate test in school laboratories where 
platinum is not available, the following alternative method 
may be used: 

Dissolve about 0.1 gram pure hematoxylin in 25 c.c. 
water ; this solution will keep for two weeks and works best 



water: analytical methods. 139 

after being made several hours. To 50 c.c. of the water, 
placed in a four-inch porcelain dish, add two drops of the 
haematoxylin solution, allow the solution to stand for one 
or two minutes, then add a drop of 20 per cent, acetic acid. 
The standards are prepared at the same time, using 50 c.c- 
of distilled water and the required amount of a stand- 
ard alum solution. The comparison must be made imme- 
diately, since the color fades on standing. In this way the 
presence of one part of aluminum sulphate in five million can 
be determined directly in the water and with ease. 

Logwood may be used instead of the haematoxylin, the 
solution being prepared as above. 

Notes. — This test will show the presence of all soluble salts 
of aluminum which enter into combination with the coloring 
matter of the logwood to form a " lake." 

The alkalies and alkaline earths give a purplish color with 
logwood extract, hence the test for alum can be made only in 
acid solution. 

Determination of Lead. — Lead in the minute quantities 
in which it ordinarily occurs in water is best estimated by 
comparing the color of the sulphide with standards. 

Directions. — If the water is colorless, acidify the clear solu- 
tion, concentrated if need be, with two or three drops of 
acetic acid, and pass in hydrogen sulphide to saturation. If 
a color is produced, compare it in a 100-c.c. tube with the 
color given by varying quantities of a standard lead solution. 

If the water is too highly colored to estimate the lead di- 
rectly, evaporate three or four liters in a porcelain dish to 
about 25 c.c, add 10 c.c. of ammonium chloride solution and 
a considerable excess of strong ammonia. Then add hydro- 
gen sulphide water and allow the dish to stand some hours. 
JBoil the contents of the dish for a few moments to expel the 



140 AIR, WATER, AND FOOD. 

excess of hydrogen sulphide, and filter. The precipitate con- 
tains all the lead, iron, and suspended organic matter, also 
copper and zinc if present, while the soluble color goes into 
the filtrate. Wash once with hot water, transfer the filter to 
the original dish, and dissolve the sulphides by boiling with 
dilute nitric acid (i part acid, sp. gr. 1.2, to 5 parts water). 
Filter and wash; evaporate to 10-15 c.c, cool, add 5 c.c. con- 
centrated sulphuric acid and evaporate until copious fumes 
are given off". Then, if the original water contained less than 
0.25 part iron per million, add acetic acid and ammonia, boil, 
filter, and read the' amount of lead in the alkaline filtrate, 
making the standards (page 260) also alkaline with ammonia. 

If the water contained over .25 part iron, wash the lead 
sulphate into a beaker with alcohol and water, and let it set- 
tle overnight. Filter, wash free from iron with 50 per cent, 
alcohol, dissolve the precipitate by boiling with ammonium 
acetate, filter, and determine the lead as above. 

Note. — If more than .25 part of iron is present, some of 
the lead will be held by the precipitated ferric hydroxide; and 
if 25 parts are present, all of the lead may be lost in this way; 
hence the modification of the method in the presence of con- 
siderable quantities of iron.* 

When copper is also present it is detected by the blue 
color given to the ammoniacal filtrate from the iron precipi- 
tation. 

Statement of Results — In reporting water analyses the 
results are best expressed in milligrams per liter, which for 
the majority of waters is equivalent to " parts per million." 
Occasionally it may be desirable to express the results in 
" grains per gallon." Parts per million may be converted into 
grains per U. S. gallon by multiplying by 0.058. For con- 

* Ann. Rep. State Bd. Health, Mass., 1898, 577. 



water: analytical methods. 



141 



venience the results should be arranged in tabular form, such 
an arrangement being suggested below: 

sanitary water-analysis. 

(Parts per 1,000,000.) 





Date. 


Physical. 


Residue on Evaporation. 


No. 


Color. 


Turb. 


Sed. 


Odor. 


Total. 


Loss. 


Fixed. 


Change 




Cold. 


Hot. 


Ignition. 


X2I 


3-9-'oo 


.50 
0.0 
0.0 


Dec. 

None 


Cons. 

None 


None 


F. Veg. 

None 


42.5 

64.0 

9740.0 


12.5 


30.0 


(Slight 
\ black 


"3 











Nitrogen as 




No. 


Total 
Organic. 


Alb. Ammonia. 


Free Am. 


Nitrite. 


Nitrate. 


Ox. 

Cons. 




Total. 


Sol. 


Susp. 




121 


.598 


.306 
.014 
.032 


.170 


.136 


.056 
.000 
.560 


.003 
.000 
.003 


.220 
.1.40 
1. 14 


4.83 

•41 

3.23 


123 















Hardness 


Chlorine 
as 
Chlo- 
rides. 


Iron. 


Biological (per c.c.) 


No. 


Bac. 


Plants. 






Diatoms. 


Cyano- 
phyceae. 


Alg«e. 


Animals. 




20.0 

23.0 

560.0 


1.8 

6.3 

1198.0 






■ 








229 




.01 

.46 




123 























No. 121 is from a pond; 122 from a spring; 123 from an artesian well. 



CHAPTER VIII. 

FOOD IN RELATION TO HUMAN LIFE: COMPOSITION, SOURCES, 

DIETARIES. 

Life itself is conditioned on the food-supply. Wholesome food 
is a necessity for productive life. Man can and does exist on very 
unsuitable, even more or less poisonous, food, but it is merely 
existence and not effective life. This is true not only of the 
wage-earner, but of the business-man, the professional man, the 
scholar. To be well, to be able to do a day's work, is man's 
birthright. Nevertheless a too large proportion of the American 
people sells this most valuable possession for a mess of pottage 
which pleases the palate for three minutes and weights the diges- 
tive organs for three hours. With the products of the world ex- 
posed in our markets, the restraints of a restricted choice, as well 
as inherited instincts or traditions, lose their force. The buyer, 
unless he has actual knowledge to guide him, is swayed by the 
caprices of the moment or the condition of his purse, and often 
fails to secure adequate return in nutritive value for the money 
paid. The fact that so much manipulated material is put upon 
the market renders this choice of food doubly difficult, since the 
appearance of the original article is often entirely lost, and to 
city-bred buyers even the natural product conveys little idea of 
its money value. It is now even more necessary that an elemen- 
tary knowledge of the proximate composition and food value of 
the more common edible substances should be recognized as 

an essential part of education. 

142 



FOOD IN RELATION TO HUMAN LIFE. 1 43 

Food: Definition and Uses. — Food is that which builds up the 
body and furnishes energy for its activities: that which brings 
within reach of the living cells which form the tissues the elements 
which they need for life and growth. Only such available sub- 
stances can be called food, no matter what their chemical compo- 
sition may be. Soft coal contains carbon and hydrogen and is 
food for the furnace, but is not available for the animal body. 

This food which is taken into the body is used in various ways. 
It forms and builds up new tissues, besides repairing and making 
good the waste of tissues due to bodily activity; it is stored up in 
the body to meet a future demand; it supplies the needed heat 
by the transformation of its stored up or potential energy into the 
muscular energy required by the body; it may be used to protect 
the tissues of the body from being themselves consumed as food. 

Composition of Food. — We determine what chemical elements 
enter into the composition of the body by an analysis of the various 
organs and tissues. We learn what combinations of these ele- 
ments serve as food by determining those present in mother's milk 
and in foodstuffs which experience has proved to furnish perfect 
nutrition. From these studies it is apparent that about fifteen 
chemical elements are constant constituents of the human body; 
that about a thousand natural products are known to have food 
value; that of these, one hundred are of world-wide importance 
(see table, page 150), and that ten of them form nine-tenths of 
the food of the world. 

The composition of food, as shown by chemical analysis, is 
not, however, the only factor that must be known to determine its 
value. The digestibility of the material must be taken into account 
as well. "We live not upon what we eat, but upon what we digest." 
It is more important to know the amount of available nutrients 
than the amount of total nutrients. 

Food Principles. — W^hile the foodstuffs present great variety, 
the food principles may be grouped under four headings; 



144 AIR, WATER, AND FOOD. 

viz., nitrogenous substances or proteids, fats, carbohydrates, 
and mineral salts. Each group contains many members with 
minor but often essential differences. To make these sub- 
stances available, there is needed an ample supply of air and 
of water, — of water for solution and circulation, of air for the 
oxygen needed to liberate the stored energy of the food in the 
place where it will accomplish its purpose. 

Nitrogenous Substances. — Since, in some way as yet un- 
known to us, nitrogen is essential to living matter, such sub- 
stances as contain this element in an available form are of the 
first importance. Some, as albumen, are so closely allied to 
human protoplasm that probably they need only to be dis- 
solved to be at once assimilated. Others, as gluten and sim- 
ilar vegetable products, undergo a greater change; while still 
others, as gelatine, have a less profound but marked effect in 
protecting the tissues from waste. 

The enzymes, " ferments," in part, of the older nomencla- 
ture, are also highly nitrogenous substances present in some 
form in nearly all foodstuffs of natural origin. The nearer 
the composition of the food approaches that of the protoplas- 
mic proteid, presumably the greater its food value, since each 
cleavage, each hydrolysis, each step in the breaking down of 
the highly complex molecule, consisting of hundreds of atoms, 
is supposed to liberate the stored energy. Therefore it is not a 
matter of indifference in what form this essential is taken. So 
little is known, however, with scientific accuracy that stu- 
dents will find a fruitful field of research along these lines of 
investigation. Also together with this element, nitrogen, go 
others, in small quantity to be sure, but evidently of great 
value. Such are sulphur, iron, phosphorus. One difference 
between the several groups of proteids is seen in this com- 
bination with the metallic elements which seems to carry with 
it certain effects. Until greater progress has been made in 



FOOD IN RELATION TO HUMAN LIFE. 1 45 

determining the availability in the organism of the various 
known substances, we must be content with a wide margin 
in the calculated quantities necessary for the daily efficiency, 
except in the very few instances of nearly pure substances, as 
white of egg. It is evident also that the manner of prepara- 
tion and the kind of mixtures used in food will afreet most 
profoundly so unstable and complex a class of substances. 
One thing is certain, that the body cannot take nitrogen 
from that which does not contain it. Therefore a cer- 
tain quantity of highly nitrogenous food should form "a 
portion of the daily supply. It is usually held that the body 
seems to be sufficiently nourished when the food contains 
an amount of digestible proteid equivalent to about ioo> 
grams of dry albumen per day for the average adult, although 
recent work has shown that this figure is probably too high. 
An excess appears to have a stimulating effect and overloads 
the system with the waste, since the end-products are not 
purely mineralized substances, as are carbon dioxide and 
water from the carbohydrates, but are compounds of an or- 
ganic nature, as creatin, urea, and uric acid, which have 
deleterious effects when accumulated in the system. A de- 
ficiency of nitrogen is made good, to a limited extent, by the 
protective agency of the other foodstuffs which offer them- 
selves for all the offices except the final one of tissue-building. 
Fats. — For this protective action, as well as for many other 
purposes, the fats are most valuable, and if they occur in about 
the same proportion as do the nitrogenous elements, the 
needs of the organism seem to be well met. Thus, in mother's 
milk, in eggs, and in meat from active animals these two are 
in nearly equal proportions, while in the cereals the fat is less; 
in nuts and in meat from fattened animals, as a rule, it is 
higher than the nitrogen. Little is known as to the varying 
food value of these fats from different sources. Certain 



146 AIR, WATER, AND FOOD. 

physical conditions of solidity, melting-point, etc., seem to 
have more influence than mere chemical composition. What- 
ever the source, it is certain that the stored-up energy which 
is to serve the organism in cases of loss of income from any 
cause is in the form of fat, a form which is not subject to the 
action of agents which so readily decompose proteids and 
•carbohydrates and yet is readily converted into available food 
whenever called for. That it is not absolutely necessary that 
the food should contain fat as such seems to be proved by 
experiment, but from the fact that all nearly natural food- 
substances do contain it, and that it appears to be more 
economical of human energy to take it from these foods than 
to manufacture it from the proteids and carbohydrates, we 
may safely assume fat to be an essential of the human dietary. 

That the equality in amount of fat with nitrogenous com- 
pounds is not essential is proved by the fact that the strong 
draft animals, as horses and oxen, take food in which the per 
cent, of fat is not more than half as much as of proteid; never- 
theless it is present in the food of all animals and doubtless, 
in its turn, is protected by an excess of the third class of 
foodstuffs, the carbohydrates, characteristic of the vegetable 
kingdom — a class which in the final decomposition yield clean 
volatile products, water and carbon dioxide, and which, there- 
fore, do not clog the system so readily as do urea and other 
wastes. 

Carbohydrates. — The number of more or less well-defined 
substances under this head is legion: starches from scores 
of plants, sugars from as many more, gums, pectins, and 
dextrins, all with a certain food value, dependent prob- 
ably upon the utilization of the various mixtures with 
which they are taken into the alimentary canal. These 
foodstuffs are very liable to " fermentation," that is, to an' 
acid decomposition which prevents their absorption by 



FOOD IN RELATION TO HUMAN LIFE. 147 

the delicate lining of the walls of the intestines and which 
causes digestive disturbance. The sugars, which are very 
soluble, and therefore liable to be present in excess, are es- 
pecially subject to this change. This class of food-substances 
is found in the diet of civilized man, free to choose, in an 
amount about equal to the sum of the other two classes, with 
a tendency to less rather than more. It may be said that 
sugar and fat increase over starch in the diet of a people of 
unrestricted choice, but it is not certain that the qualities of 
body which make for hardihood and resistance to disease 
are correspondingly increased. There is, indeed, much evi- 
dence to show that power of digesting vegetable foods indi- 
cates a general well-being of body conducive to long life. A 
ready adaptation renders possible the changes of habitat re- 
quired by civilization. Unless one is to be confined to a nar- 
row range it is wise to cultivate a strength of digestion as 
well as a strength of muscle, and for the best brain power we 
believe it to be more essential. 

Mineral Salts. — The fourth class, mineral salts, comes into 
the food largely from the vegetable substances eaten, for in 
these the union is an organic one readily assimilated. As we 
have seen, certain elements go with the nitrogenous portion, 
as, for example, in gluten and its congeners are found sul- 
phur and phosphorus. Potassium, found in barley, is a con- 
stant constituent of protoplasm, while sodium is found in 
blood-serum. A lack of vegetable foods seems to impoverish 
the blood-corpuscles. For children, a deficiency in lime 
causes serious disease. Sugar, olive-oil, corn-starch, and 
other prepared food-substances cannot take the place of 
asparagus, cabbage, carrots, etc. 

To sum up briefly, then, wu may say that the protein or nitro- 
genous portion of the food forms tissue, such as muscle, sinew and 
fat, and furnishes energy in the form of heat and muscular strength ; 



I48 AIR, WATER, AND FOOD. 

the fats build up fatty tissue, but not muscle, and supply heat; the 
carbohydrates are changed into fat and supply heat. Another im- 
portant use of the nutrients is to protect each other from being used 
in the body. The carbohydrates, especially, in this way protect 
the protein, including muscle, etc., from consumption. 

Change in Composition Due to Cooking. — The composition of 
cooked food is in general not the same as the raw material on ac- 
count principally of chemical and physical changes brought about 
by the heat employed in the cooking process. The total nutrients, 
calculated on a water-free basis, may be practically the same, but 
the structure is often quite different. 

Starch is hydrolyzed and rendered soluble by heating in the 
presence of moisture, and at higher temperatures it may be con- 
verted into the brown, soluble dextrin. The sugars are changed, 
being, in the case of sucrose, partly converted into other forms, 
such as invert sugar, by the heating, with the help of the organic 
acids present in many foods. Some of the proteids tend to become 
less soluble through heating and at higher temperatures may be 
even partly decomposed with possible loss of food value. 

Heat of Combustion. — Until a more definite knowledge of the 
processes of metabolism (the transformations of matter and energy 
in the animal organism) is obtained the potential energy of food is 
calculated in terms of mechanical work — expressed in heat-units 
or calories. 

One calorie is the amount of heat required to raise the tempera- 
ture of one gram of water one degree centigrade. A gram of fat, 
as actually digested and oxidized in the body, affords enough 
heat to raise the temperature of about 9000 grams of water one 
degree. In like manner a gram of protein has an energy- 
producing power expressed in calories of about 4000, and for 
carbohydrates the average value is also 4000. 

Allowance is made in these figures for the fact that to digest com- 
pletely any part of our food results in a decrease of the amount of 



FOOD IN RELATION TO HUMAN LIFE. 1 49 

energy to be derived from it, and this affects the protein more than 
it does the other two. It is probably true that under favorable con- 
ditions the fat and carbohydrates can be completely utilized in the 
body and consequently their energy-producing power can be correctly 
estimated from their heat-producing power outside the body, In 
the case of protein, however, the digestion within the body is never 
so complete as to furnish all the energy that would be obtained by 
a complete combustion of these nitrogenous materials outside of 
the body. 

The fact remains, however, that all experiments yet made go 
to show that within practical limits We are safe in using the heat 
of combustion (expressed in calories) of any food-substance at a 
controlling measure of food values. 

Nutritive Ratio. — The requisite number of calories must, how- 
ever, be obtained by the utilization of such substances as contain 
all the elements needed by the body, and in such ratio as has been 
found available for the balance of nutrition. In carrying on its 
multifarious activities the body loses about 20 grams of nitrogen 
per day, which must be replaced by the same element in the food 
taken. Thus while the requisite number of calories may be fur- 
nished by fat or starch, these substances alone will not suffice for 
complete nutrition. The nutritive ratio, or the proportion of 
nitrogeneous to non-nitrogenous food, must be maintained in the 
proportion of 1 to 3, or at least 1 to 5. 

The following table of one hundred common food-mate- 
rials is arranged in the order of calorific or energy-giving 
power, but in considering the food value of any one substance 
its nitrogen content must also be considered, and such com- 
binations made as will yield the requisite elements for a well- 
oalanced ration. 

From even a cursory examination of the table it will be 
seen how widely some of the foodstuffs differ under differing 
conditions of soil moisture, fertilization in the case of plants, 



J5o 



AIR, WATER, AND FOOD. 



COMPOSITION OF SOME COMMON FOOD-MATERIALS AS PURCHASED* 
I. Fuel Value 3000-4000 Calories* per Pound. 



Food -material. 



Butter 

Lard (refined) 

Oleomargarine. . . . 

Salt fat pork 

Suet 

Walnuts (shelled) 



Refuse. 



Per cent. 



Water. 



Per cent. 



I I o 



9-5 
0.3 to 12.2 
4.3 t° 21 9 

3-5 



Nitroge- 
nous 
Substances. 



Per cent. 



0.2 to 5.0 

i.r to 7.5 

16.6 



Fat. 



Per cent. 

85.0 
100.00 

83.0 
80.3 to 94.1 
70.7 to 94.5 

63.4 



Carbo- 
hydrates. 



II. Fuel Value 2000-3000 Calories per Pound. 



Bacon 

Cheese (American pale). 

Chocolate 

Doughnuts 

Mutton Hank (fat) 

Peanut butter 

Sausage (farmer) 



8.7 



3 9 



10.4 
31.6 
,5 to 10.5 
o to 25.8 
28.9 

2.1 
22.2 



9-5 

28.8 

12.5 to 13.4 

5.1 to 7.6 

10.7 

20 3 
27.9 



59-4 

35-9 
47.1 to 50.2 
16.4 to 25.7 

59.8 
46.5 

40.4 



III. Fuel Value 1500-2000 Calories per Pound. 



Barley (pearled) 

Beans (dried) 

Cake average (except fruit). 

Candy 

Cheese (Neuchatel) 

Corn-meal 

Corn-starch 

Crackers (average) 

Fat meats 

Gelatin 

Ham (smoked, medium fat) 
Infants' and invalids' foods 

Macaroni 

Oats 

Peanuts 

Peas (dried) 

Pop-corn 

Rice 

Rye flour 

Sugar (granulated) 

Wheat (entire) flour 

Wheat flour (white bakers'). 

Wheat (shredded) 

Zwieback 



11. 7 



4.5 to 28.4 



9.8 to 12.9 I 

9.6 to 15. 5 

19.9 

4.0 

42.7 to 57.2 

8.8 to 17.9 
10. o 

6.8 

38.3 

13.6 
27.3 to 42.5 
2.4 to 12.3 

7.0 to 12.3 

7.8 
6.9 

6.9 to 15.0 

4-3 

9.1 to 14.0 
11. 9 to 13 6 



7.0 to 10. 1 

19.9 to 26.6 

6.3 



6.4 to 13.1 
lo.i to 13.3 
7.2 to 10.7 
5.0 to 7.7 

* Including fibre. 



15. 1 to 22.3 
6.7 to 11.6 

10.7 
13.0 
84.2 

10.2 to 21.9 
2.0 to 22.5 
7.9 to 16.6 

16. s 

19. 5 
20.4 to 28.0 

10 7 
5.9 to 11.3 
4.9 to 8.8 



12.2 to 14.6 
10.3 to 14.9 
9.6 to 11. 4 
8.6 to 11. 7 



0.7 to 1.5 

1 4 to 3.1 

9.0 



22.3 to 32.5 
1.0 to 5.3 



24.5 to 39.9 
0.3 to 10.9 
0.0 to 4.9 

7-3 

29.1 

0.8 to 1.3 

5.0 

0.1 to 0.7 
0.2 to 1.3 



Perci 



26.8 to 33.8. 
45.8 to 63.2 



.5 to 2.1 
.9 to 2.0 
.3 to 1.6 
.1 to 1 1. 3 



[7.1 



77.3 to 78.1* 
57.2 to 63.5* 

63-3 

96.0 

2 tO 2.9 

68.4 to 80.6* 
90 o* 

71.9* 



66.9 to 89.4 

67.2 to 78.4*. 

66.5* 

18. 5 
58.0 to 67.4* 

78.7 

75.4 to 81.9* 
77.6 to 80.2* 

IOO 

69.5 to 77.0* 

70.3 to 75.5 
75.0 to 79.7* 

72.1 to 74.2 



IV. Fuel Value 1000-1500 Calories per Pound. 



Apples (dried) 

Bread (white) 

Corn-bread 

Dates 

Figs 

Fresh pork (ribs and shoulder). 
Medium fat mutton and beef... 

Mince-meat (commercial) 

Mince-meat (home-made) .. ., 

Pies 

Prunes (dried) 

Raisins , 

Sandwiches 

Sardines (canned) 

Salt mackerel 



[5.9 to 20.3 
[4.4 to 27.8 



15.0 

IO. o 



5-o 

22.9 



8. 


6 to 47.4 




35.3 


28 


4 10 48.0 




1.3.8 


1 1 


6 to 25.0 


4° 


.1 to 43.6 


3« 


to 44.9 




27.7 




54-4 




44.9 




19.0 




13 1 




44-9 




53 6 




32.5 



T 


2 to 2.5 


6 


9.2 
5 to io.'i 


2 


i-9 

.6 to 5.7 


1- 


.710 14.5 
.4 to 12.9 

6.7 
4.8 




4.4 
1.8 




»-3 




10.9 




23-7 
16.3 



0.1 to 5.0 

»-3 

2.3 to 9.8 

2.5 
0.3 

25.4 to 25.6 
19.8 to 31.2 

14 

6.7 

9.4 

30 
9.0 



48.6 to 86.91. 

53.1 
40.31054.3 

70.6 
68.3 to 83.1 



60.2 

32.1 

39-2 
62.2 
68.5 
33-3 



* One Calorie equals 1000 calories. 



FOOD IN RELATION TO HUMAN LIFE. 



I5F 



COMPOSITION OF SOME COMMON FOOD MATERIALS. — Continued. 
V. Fuel Value 500-1000 Calories pek Pound. 



Food-material. 



Beef (round) 

Beef (sirloin steak). 
Chicken (fowls) . . . 

Cream 

Eggs 

Herring (smoked) . 

Meats (lean) 

Olives 

Salmon (fresh) . . . 
Salmon (canned)... 
Tapioca pudding. . 

Tongue (beef) 

Turkey 

Veal (breast) 



Refuse. 



Per cent. 

8.5 

12.8 

18.0 to 42.7 



44-4 
0.5 to 11. 3 

19.0 
23.8 to 35.:. 
11. 7 to 16.9 



9.2 to 55 3 
17.1 to 32.4 
15.7 to 25.4 



Water. 



Per cent. 

62.5 

54.0 
38 3 to 53.7 

74.0 

65-5 

19.2 
59.9 to 69.2 

52.4 

45.0 to 51.2 
54.6 to 58.2 
52.0 to 71.6 

32.4 to 69.2 

41. 1 1044.7 

48.5 to 55.7 



Nitroge- 
nous 
Substances. 



Per cent. 
19.2 
16.5 

11. 5 to 16.0 

2-5 

11.9 
20.5 

18. 1 to 21.4 
i-4 

12.6 to 15.0 
18.6 to 20.2 

2.8 to 4.2 
7.8 to 20.2 
15.8 to 16.8 

14.2 to 16.9 



Fat. 



Per cent. 

9.2 

16. 1 

6.9 to 21.5 

18.5 
9-3 
8.8 

7.8 to 14.2 
21.0 

6.6 to 9.5 
5.6 to 9.8 

2.3 to 4.8 
0.7 to 15.3 

5.9 to 25.5 

9.4 to 12.8 



Carbo- 
hydrates. 



Per cent. 



21.9 to 38.1 



VI. Fuel Value 400-500 Calories per Pound. 



Beans (canned red kidney). 

Calf 's-foot jelly 

Salt cod (boneless) 

Succotash (canned) 

Sweet potatoes 



1.6 
20.0 



72.7 
77-6 
54-8 
71.4 to 79.9 
55-2 



VII. Fuel Value 300-400 Calories per 



Bananas .. . 
Butter beans 
Fish (fresh) . 

Grapes 

Hash 

Milk 

Potatoes . 



3 r -o 
50.0 

25.2 to 46.0 
25.0 



48.9 
29.4 
46.1 to 49.1 
58.0 
80.3 
87.0 
62.6 



7.0 


0.2 


18.5 


4-3 




17 4 


27.7 
2.9 to 4.4 


o-3 
0.7 to 1.7 




14.9 to 22.4. 


i-4 


0.6 


21.9 


[ES PER 


Pound. 




8 


°-4 


14-3 


4-7 


o-3 


14.6 


1.9 to 12.0 


1.8 to 5.9 




1.0 


1.2 


14.4 


6.0 


1-9 


9-4 


3-3 


4.0 


5-o 


1.8 


O.I 


14.7 



VIII. Fuel Value 2^0-300 Calories per Pound. 



Apples 

Chicken (broilers) 

Cranberries 

Onions . 

Oysters (solid) . . . 

Parsnips , 

Pears 



25.0 
3*-4 to 55. 



20.0 
10. o 



63.3 
44-6 to 52.4 
87.6 to 89.5 

78.9 

82.2 to 92.4 

66.4 

76.0 



9.0 to 15.7 
0.4 to 0.5 

1.4 

4-5 to 7.3 
i-3 
o-5 



to 1 
to c 

o-3 
to 1 
0.4 
0.4 



10.8 



IX. Fuel Value 100-200 Calories per Pound. 



Beets 

Cabbage 

Carrots 

Green corn ... 

Lemons 

Oranges 

Soups (canned) 

Spinach , 

Squash 

Tomatoes (canned). 



70.0 

77 7 

70.6 

29.4 

62.5 

6^.4 
91.0 to 92.8 
91.6 to 92.8 

44 2 

92.5 to 07.9 



O.7 

0.6 

2.9 to 5.0 
1.8 to 2.4 

o 7 
0.3 to 1.7 



0.5 



to 0-8 
to 0.5 



9.3 to 10.9 

8.9 

1.5 to 6.2 

10.8 



7-7 

4.8 

7-4 

7-7 

5-9 

8.5 
0.6 to 5.7 
3.1 to 3.4 

4-5 
1.4 to 8.1 



X. Fuel Value 10-100 Calories per Pound. 



Asparagus 

Bouillon (canned) 

Celery 

Cucumbers 

Watermelons 



20.0 
15.0 
59-4 



94.0 

96.5 to 96.7 

75-6 



.7 to 2.6 
0.9 
0.7 
0.2 



0.2 
0.0 to 0.2 



0.2 

O.I 



3-3 

to 0.3 
2.6 
2.6 



i5 2 



AIR, WATER, AND FOOD 



and of fatness or leanness in animals, of method of prepara- 
tion or of combination in cooked foods. 

Therefore examinations of materials are imperative if 
there is to be any basis of calculation. In an institution where, 
for instance, flour forms two-thirds of the daily ration, if it 
contains the lowest per cent, of nitrogen it may not furnish 
sufficient proteid for a well-balanced ration, or if the meat 
used is very lean there may not be fat enough for the best nu- 
trition. 

The great variation in the proportion of water leads to 
many surprises, and the amount of unedible material is to be 
considered. The uneducated provider buys oysters under the 
impression that he is furnishing food of high value, and does 
not distinguish between potatoes and rice. 

In the present state of our knowledge, the best use to 
which we can put such tables and analyses is as a check 
against gross errors of diet, which are found with alarming 
frequency especially among children and students, those who 
can least afford to make them. References will be found in 
the Bibliography to works for further study along these lines. 

Dietaries. — A dietary is simply a known amount of food of 
known composition per person per day, week, or month. 

What is called a standard dietary is such a combination of 
food-materials as shall furnish the amounts held to be neces- 
sary. The following are examples of such standard dietaries: 



Approximate Amounts 
required daily by 


Nitrogenous, 
grams. 


Fats, 
grams. 


Carbohydrates, 
grams. 


Calortes. 




62 

78 

IOO 

IOO 

125 


45 
45 
75 
90 

125 


200 
28l 
380 
450 
500 


1593 
1890 
2665 
3092 
3725 






Adult at moderate work 
Adult at hard work... 



(In feeding experiments from 10 to 20 per cent, more must be allowed 
for waste and indigestibility.) 



FOOD IN RELATION TO HUMAN LIFE. 1 53 

From the table on p. 150 may be selected such food as will 
give the required quantities in variety enough to suit any taste. 
That which the table cannot give is the per cent, of each which, 
tinder any given condition, will be utilized by the person fed. 
The strength of the digestive juices, exercise, fresh air, the 
cooking, the mixing of the foods, the habits of mind as to 
food, the customs of the family, all influence this utilization, 
so that other means must be resorted to in order to gain an 
idea of what is practicable. This is done by taking account 
of the food of persons free to choose ; of those in different 
countries, in different circumstances, and using a great 
variety of materials. Since Voit made his standard dietary in 
1870, many hundreds, at least, have been so gathered in the 
United States alone — more than two hundred since 1886. All 
the information thus gained goes to confirm the theoretical 
standard, and also to show how much depends upon suitable 
preparation and combination. These last two things help 
each other. 

As food is ordinarily prepared, about 10 per cent, must 
be deducted for indigestibility in a customary mixed diet, and 
about 10 per cent, more for the refuse or waste of food as 
purchased, so that of the total pounds of meat, vegetables, 
and groceries some 20 per cent, is of no final service in the 
body. It is immaterial whether this amount is subtracted 
from the final calculation or whether the higher figures be 
taken, that is, whether 125 grams of proteid as purchased or 
100 grams final utility is used. There will be an unknown 
limit in either case. According to late experiments 100 
grams of proteid is high. The waste of fats is less in propor- 
tion as the dietary is a restricted one. 

Knowledge of Food Values Necessary. — The most serious 
aspect of the food question is that the taking of it is volun- 
tary, not, like air, a necessity beyond control, and that the 



154 a: 

most fantastic ideas are allowed to rule. The day-laborer is 
in little danger, since his food demand is made strong by out- 
of-door exercise; but the student who shuts himself up in 
hot, close rooms, and who does not look upon food as his 
capital, but only as a disagreeable task or an amusement, is in 
great danger, as is he who, having heard that one can live on 
a few cents a day, proceeds to try it without knowledge, and 
suffers a loss of efficiency for years or for all his life. 

It is not nearly so difficult to acquire a working knowl- 
edge of food values as of whist or golf, so that on entering a 
restaurant a suitable menu may be made up within one's al- 
lowance. It is only necessary to correct prevailing impres- 
sions and reinforce one's experience. 

Figs, dates, raisins, and prunes are apt to be regarded as 
luxuries instead of as rich food-substances of a most di- 
gestible kind when freed from skin and seed. Nuts are a 
much neglected form of wholesome food, admirably suited 
to a winter table from their richness in fat, and also furnish- 
ing muscular energy, as is seen in the agile squirrel, and is 
proved by many human examples. With nuts, however, 
must be taken fruits or other bulky foods, to balance the con- 
centration. The somewhat compact and oily substance must 
be finely divided and freed from its astringent skin. 

In distinction from these rich foodstuffs, we find oranges, 
apples, etc.; the usual garden vegetables, asparagus, lettuce, 
etc., which, while they fill an important place in the dietary, 
add little directly to the energy of the 'body and need not be 
considered except as, by their flavor or aesthetic stimulus, 
they add to the efficiency of the rest. 

The foods which furnish the greatest nutrition for the least 
money are such materials as corn meal, wheat flour, milk, 
beans, cheese and sugar. The expensive cuts of meat, high- 
priced breakfast cereals and the like, add but little to the 



FOOD IN RELATION TO HUMAN LIFE. 1 55 

nutritive value but greatly increase the cost of living. A meal of 
lettuce dressed with oil, eaten with bread and cheese, fulfils all the 
requirements of nutrition, and may cost five cents. The same 
food value from sweet breads, grape-fruit, etc., might cost a dollar. 
Incorrect ideas in regard to food values, and prejudice inherited or 
acquired against certain foods, have too often resulted in exclud- 
ing wholesome and nutritious articles from the dietary and de- 
creasing thereby the efficiency of the human machine. 



CHAPTER IX. 

THE PROBLEM OF SAFE FOOD. ADULTERATION AND SOPHISTICATION. 

Adulteration grows largely, if not almost entirely, from exces- 
sive competition. Nearly every article of common food has been 
found at one time or another to be adulterated, yet manufacturers 
testify that they willingly would stop this addition of foreign 
material if they could be sure that their competitors would stop 
also. Other causes there are also: the demand for goods out of 
season; for perishable products which must come many miles; 
the failure of the supply of a given substance to meet a continu- 
ing demand; all of these lead to adulteration, imitation and sub- 
stitution. 

To many people otherwise intelligent, the term adulterated food 
is synonymous with poisoned food. With others, thanks to alarm- 
ing newspaper articles, not wholly disinterested, the general im- 
pression is far beyond the reality. It is not necessary to use poison- 
ous or even deleterious material : it needs only to mix with the food 
material some substance cheaper but harmless, to make some 
change in the outward appearance of the article so that people 
shall not recognize the familiar substance, and then to herald far 
and wide the discovery of a new process by which the food value 
is greatly enhanced. "Things are not what they seem" is nowhere 
more true than in the case of foods. 

Definition of Adulteration. — To adulterate is "to debase" "to 
make impure by an admixture of baser materials." The word 
"adulterated refers to any food to which any foreign substance, 
not a proper portion of the food, has been added. It does not 

156 



THE PROBLEM OF SAFE FOOD. T57 

matter whether the added material is of greater value than the 
food itself. The addition of coffee to cereal or substitute coffees, 
is properly held to be an adulteration. Deterioration should not 
be mistaken for adulteration. People who are not wholly familiar 
with the appearance of a food or the chemical and physical changes 
which it may undergo, think that if it does not taste just right or 
look just right that it must be adulterated. Appearance has slight 
relation to the purity of the article in these days of paint, polish 
and powder. 

Some forms of adulteration are more properly described under 
the head of misbranding, that is, referring to foods incorrectly de- 
scribed by the label. While the significance is not exactly the 
same as that of the word adulterated, yet the two may sometimes 
be applied to the same product. For instance, the addition of 
starch to sausage to conceal the use of excessive amounts of water 
and of fat constitutes an adulteration, which would not be the case 
if the article were properly branded to show the presence of the 
added "filler." 

To adulterate the coin of the realm or the liquor of the bar with 
a baser metal or an imitation whisky is a heinous offence. So is 
the mixture of milk with the baser article, water, which thereby 
lowers its food value. But the " wretched sophistry" which ob- 
scures the nature of things on a package of prepared food mis- 
leads more persons and inflicts more injury upon the community 
than the other, yet goes unrebuked. The most barefaced asser- 
tions are printed in magazines, and "pure-food shows" only whet 
the appetite for something new. 

Legal Definition of Adulteration and Misbranding. — In the 
Federal Pure Food Law, commonly known as the Food and Drugs 
Act of June 30, 1906, adulteration and misbranding are thus 
defined : 

Sec. 7. That for the purposes of this Act an article shall be 
deemed to be adulterated : 



158 AIR, WATER, AND FOOD. 

In the case of food : 

First. If any substance has been mixed and pacjked with it so 
■as to reduce or lower or injuriously affect its quality or strength. 

Second. If any substance has been substituted wholly or in 
part for the article. 

Third. If any valuable constituent of the article has been 
wholly or in part abstracted. 

Fourth. If it be mixed, colored, powdered, coated, or stained 
in a manner whereby damage or inferiority is concealed. 

Fifth. If it contains any added poisonous or other added dele- 
terious ingredient which may render such article injurious to 
health: Provided, That when in the preparation of food products 
for shipment they are preserved by any external application applied 
in such manner that the preservative is necessarily removed me- 
chanically, or by maceration in water, or otherwise, and directions 
for the removal of said preservative shall be printed on the covering 
or the package, the provisions of this Act shall be construed as 
applying only when said products are ready for consumption. 

Sixth. If it consists in whole or in part of a filthy, decomposed, 
or putrid animal or vegetable substance, or any portion of an animal 
unfit for food, whether manufactured or not, or if it is the product 
of a deceased animal, or one that has died otherwise than by 
slaughter. 

Sec. 8. That the term " misbranded," as used herein, shall 
apply to all drugs, or articles of food, or articles which enter into 
the composition of food, the package or label of which shall bear 
any statement, design, or device regarding such article, or the 
ingredients or substances contained therein which shall be false or 
misleading in any particular, and to any food or drug product 
which is falsely branded as to the State, Territory, or country in 
which it is manufactured or produced. 

That for the purposes of this Act an article shall also be deemed 
to be misbranded : 



THE PROBLEM OF SAFE FOOD. 1 59 

In the case of food : 

First. If it be an imitation of or offered for sale under the dis- 
tinctive name of another article. 

Second. If it be labeled or branded so as to deceive or mislead 
the purchaser, or purport to be a foreign product when not so, 
or if the contents of the package as originally put up shall have 
been removed, in whole or in part, and other contents shall have 
been placed in such package, or if it fail to bear a statement on 
the label of the quantity or proportion of any morphine, opium, 
cocaine, heroin, alpha or beta eucaine, chloroform, cannabis indica, 
chloral hydrate, or acetanilide, or any derivative or preparation of 
any of such substances contained therein. 

Third. If in package form, and the contents are stated in terms 
of weight or measure, they are not plainly and correctly stated on 
the outside of the package. 

Fourth. If the package containing it or its label shall bear any 
statement, design, or device regarding the ingredients or the sub- 
stances contained therein, which statement, design, or device shall 
be false or misleading in any particular: Provided, That an article 
of food which does not contain any added poisonous or deleterious 
ingredients shall not be deemed to be adulterated or misbranded 
in the following cases: 

First. In the case of mixtures or compounds which may be 
now or from time to time hereafter known as articles of food, 
under their own distinctive names, and not an imitation of or 
offered for sale under the distinctive name of another article, if 
the name be accompanied on the same label or brand with a state- 
ment of the place where said article has been manufactured or 
produced. 

Second. In the case of articles labeled, branded, or tagged 
so as to plainly indicate that they are compounds, imitations, or 
blends, and the word "compound," "imitation," or "blend," as 
the case may be, is plainly stated on the package in which it is 



l6o AIR, WATER, AND FOOD. 

offered for sale: Provided, That the term blend as used herein 
shall be construed to mean a mixture of like substances, not ex- 
cluding harmless coloring or flavoring ingredients used for the 
purpose of coloring and flavoring only: And provided further , That 
nothing in this act shall be construed as requiring or compelling 
proprietors or manufacturers of proprietary foods which contain 
no unwholesome added ingredient to disclose their trade formulas, 
except in so far as the provisions of this act may require to secure 
freedom from adulteration or misbranding. 

Extent of Adulteration. — In any discussion of the extent to 
which adulterated foods are sold it must be borne in mind that 
the adulterated articles make up only a relatively small proportion 
of the food that actually passes over the counter. Flour, for ex- 
ample, is seldom adulterated ; pepper, mustard and vanilla extract 
often are. For one pound of these substances sold, iooo pounds 
or more of flour go out from the store. Figures given in official 
reports of food inspection do not represent the case exactly, be- 
cause the inspectors are trained men, and purchase samples of 
those lines of goods which experience has shown them to be most 
likely to be adulterated. Brands of foods which they have reason 
to believe are pure they do not sample. Estimated on the total 
quantity sold, it is doubtful if more than 5 to 10 per cent, of the 
food sold is adulterated in any way, and these figures would un- 
doubtedly be much too high for those states in which there is a 
well-enforced system of food inspection. 

Character of Adulteration. — Much of the present propaganda 
in the interests of pure food and the movement for the protection 
of the consumer can be summed up in three words: "An Honest 
Label." In many cases an accurate and true statement of the 
contents of the can or package is the only protection needed by 
the consumer, and is fully as efficient as well as much cheaper 
than prosecutions or restrictive measures. Many of the terms 
used on food packages deceive only the ignorant purchaser. 



THE PROBLEM OF SAFE FOOD. l6l 

"Strictly pure" is a well-understood trade term, with a meaning 
known to the initiated; the words " Home-Made" may cover 
some of the most highly developed products of synthetic organic 
chemistry. 

The cases in which the adulteration is of a character dele- 
terious to health are fortunately few. The use of canned goods 
brings certain dangers in the dissolved metals from the cans or 
from the solder, also from a careless habit of allowing food to 
stand in the opened tins. The liking for bright green pickles and 
peas leads to coloration by copper salts. 

So rapidly do new substances come upon the market that it is 
of little use to put into a general text-book definite statements of 
the quality of many foods. A baking-powder or a spice which is 
honestly made to-day may next week pass into the hands of un- 
scrupulous dealers who please the public and thereby salve their 
consciences. 

To furnish what the people think they want has been the rule 
from the days of an earlier generation of grocers, who divided a 
barrel of cooking-soda in halves and set one-half on one side of 
the store for "saleratus" and the other on the opposite side for 
soda, so that there should be no suspicion in the mind of the cus- 
tomer that the packages came from the same barrel, and yet each 
might satisfy his individual preference. 

Names that have passed down from a former generation as 
being above reproach are now found to cover adulterated goods. 
The trademark has passed into other and less scrupulous hands, 
and the new owners do not hesitate to trade upon the reputation 
earned by their predecessors. There are, however, several phases 
of the subject that should be briefly mentioned. 

Breakfast Foods, — The craving for something new to stimulate 
a jaded appetite already spoiled by endless variety and bad com- 
binations has led to the manufacture of a cereal preparation for 
nearly every day in the year, regarding some of which the state- 



1 62 AIR, WATER, AND FOOD. 

ment is made that they are "predigested." No better comment- 
ary on the laziness or wilful ignorance of American providers could 
be made than this. Little do the people know about wheat or 
cooking if they suppose that grain can be changed by manipula- 
tion in any kind of machine so as to give greater food value than 
was contained in the grain. While it is true that some of these 
preparations are far better than the half-cooked grains found on 
so many tables, the fact remains that it is the cook and not the 
substance which is poor. The false statements on food packages 
of all kinds are so absurd that they would defeat their own pur- 
pose were they viewed in the light of common sense. It is not 
always best to have food which is too easily digested. 

A predigested food is quickly absorbed into the circulation, 
and hence a small quantity causes a sensation of fulness and satis- 
faction, which, however, soon passes away and a faintness results. 
This is especially true of the sugars and dextrins. Frequent meals 
should go with easily absorbed foods. The rapid digestion is the 
cause of much pernicious eating of sweets between meals, which 
satisfies the appetite for the time being and prevents substantial 
quantities of other foods being taken at the time they are offered. 

From a study of analyses of a large number of foods the fol- 
lowing conclusions are drawn by F. W. Robison : * 

i. The breakfast foods are legitimate and valuable foods. 

2. Predigestion has been carried on in the majority of them 
to a limited degree only. 

3. The price for which they are sold is as a rule excessive and 
not in keeping with their nutritive values. 

4. They contain as a rule, considerable fibre which, while prob- 
ably rendering them less digestible, at the same time, may render 
them more wholesome to the average person. 

5. The claims made for many of them are not warranted by 
the facts. 

* Mich. Agr. Expt. Sta., Bull. 211 (1904). 



THE PROBLEM OF SAFE FOOD. 1 63 

6. The claim that they are far more nutritious than the wheat 
and grains from which they are made is not substantiated. 

7. They are palatable as a rule and pleasing to the eye. 

8. The digestibility of these products as compared with highly 
milled goods, while probably favorable to the latter, does not give 
due credit to the former, because of the healthful influence of the 
fibre and mineral matter in the breakfast foods. 

9. Rolled oats or oatmeal as a source of protein and of fuel is 
ahead of the wheat preparations, excepting of course the special 
gluten foods, which are manifestly in a different class. 

In general, the cost of these foods is low if they are considered 
merely as confections to please the taste, but they are expensive 
foods regarded as substitutes for the ordinary cereal products. 

This is well shown in the following table in which the fuel 
value of breakfast foods and other common food products is 
graphically compared. 

Colors and Preservatives in Food. — For many years such sub- 
stances as alcohol, vinegar, sugar, salt, and the like, have been 
used to preserve food. Such materials are commonly held to be 
harmless to persons of sound digestion if used in moderate amounts. 
Within recent years, however, there has been a constantly increas- 
ing tendency toward the use in food products of such powerful 
antiseptics as formaldehyde, salicylic and benzoic acids and their 
salts, and boric acid. An important distinction to be borne in 
mind between this class of preservatives and those first named is 
that the former when used in food in quantity sufficient to pre- 
serve it make their presence known to the consumer by either 
their taste or odor. With the chemical preservatives, however, 
an intimation of their presence is conveyed to the consumer only 
by a statement on the label. It is the general feeling among those 
engaged in the enforcement of the food laws that the common 
use of these preservatives should be forbidden, or that they should 
be allowed only under certain definite restrictions. The question 



164 



AIR, WATER, AND FOOD. 










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THE PROBLEM OF SAFE FOOD. 165 

is not one of their possible harmful effect only, although it cannot 
be successfully denied that their unrestricted use would lead to 
grave danger to health, especially in the case of invalids and chil- 
dren, or those with various degrees of digestive efficiency. It 
seems reasonable to infer that the processes of digestion being 
largely the result of bacterial and enzymic action, will be retarded 
or interfered with to a greater or less extent by substances which 
inhibit bacterial action in food. 

There is, however, another reason for objecting to the use of 
chemical preservatives. By their use much food that is unwhole- 
some and unfit for consumption can be, and is placed upon the 
market with no warning to the consumer. "The man who adds 
formaldehyde to his milk takes down the danger signal, but does 
not remove the danger." 

Similarly, objections can be made to the use of coal-tar colors 
in foods. There are hundreds of food packages which would 
never leave the grocers' shelves were it not for the fact that by 
the use of artificial color their true composition and the actual 
nature of the materials from which they are made is hidden. 
Apart from any question as to the harmfulness of these dyes, 
there is ample reason for their use being strictly regulated by 
official action, in that their use except under such supervision 
allows the manufacturer to sell inferior articles under the appear- 
ance of standard foods; it permits the customer to be misled as 
to the strength and purity of the product that he buys; the age and 
past history of the product may be made a sealed book; finally, 
by the use of coloring, an unwholesome and improper food may 
be put upon the market. 

Summary. — The chief dangers in food are from wrong pro- 
portions of proteid, fat, and carbohydrates, from fermentable and 
irritating decompositions, from bad methods of cooking and un- 
suitable combinations, from transmission of micro-organisms either 
by exposure to dust or by contact with filthy hands or vessels, to a 



1 66 AIR, WATER, AND FOOD. 

favorable medium for the growth of pathogenic germs, from un- 
suitable food scientifically disguised. 

From this hasty survey it will be seen how little danger to 
health is incurred if only reasonable care is taken and if the always 
doubtful articles are avoided. 

Take, for instance, that most commonly adulterated class, 
spices. Who will say that it may not be better to eat corn and 
buckwheat and ground peas than pure pepper? Rice is certainly 
a more wholesome food than ginger, and starch than soda. Glu- 
cose is even more easily absorbed than cane-sugar. These are 
cases of frauds on the pockets, but possibly blessings in disguise 
for the stomachs. When any community is so ignorant as to per- 
mit of such glaring cases of adulteration as coal-tar dyes in food, 
and gypsum in cream of tartar, they deserve to suffer. It is 
knowledge on the part of each intelligent citizen, which will mend 
matters, even it it is only that kind of empirical knowledge that 
one is forced to learn in relation to electricity and steam in order 
to live in a modern house. 

This knowledge is now easily obtained through the city, state 
and governmental laboratories, and their publications are acces- 
sible to all who can read and write. There is therefore no excuse 
for general ignorance and credulity as to trade preparations of 
foods, any more than for the degrading habit of purchasing patent 
medicines to remedy the ills caused by the misuse of food. Both 
together form the saddest commentary on human weakness and 
lack of rational thought. 



CHAPTER X. 



ANALYTICAL METHODS. 



In the discussion of the methods employed for the ex- 
amination of food-materials, only a few typical substances 
have been considered, and the processes given are such as to 
bring into prominence the scientific aspect rather than the 
technical detail of the subject; at the same time it is hoped 
that a sufficient variety of methods is given to enable 
the student to gain considerable experience in the necessarily 
short time which can be allotted to the subject. 

Both on account of its importance as a food-material and 
on account of its availability for the various tests, milk has 
been chosen as a type of animal food; moreover, it may be 
made to serve as an excellent example of the changes to 
which food-materials are liable through the growth of the 
micro-organisms. The analysis of milk includes determina- 
tions of specific gravity, water, or total solids, ash, fat, nitro- 
gen, and sugar, the separation of casein and albumin, and the 
detection of preservatives and coloring matters. 

The breakfast cereals are taken as typical of vegetable 
foods. The examination which may be made of this class 
includes the determination of moisture, ash, fat, nitrogen and 
proteids, starch, cellulose, and the products of peptonization 
and saccharification. 

The nature and composition of the various fats and oils 

is briefly illustrated by the examination of butter and the 

determination of the principal constants of the butter-fat. 

167 



1.6S AIR, WATER, AND FOOD. 

The results of fermentation are illustrated by the deter- 
mination of alcohol in beer, wine, meat extracts, patent medi- 
cines and " temperance drinks," flavoring essences and the 
like. The determination of the relative proportion of volatile 
and fixed acids, of the saccharine products of malting, and 
of volatile oils or flavoring principles, is also instructive. 

A more elaborate discussion of the methods used in food 
analysis and of the interpretation of results will be found in 
the larger works upon the subject. As reference books for the 
use of the student in the laboratory, the following in the 
author's experience, have been found especially helpful: Leach: 
Food Inspection and Analysis; Gill: Handbook of Oil Analysis; 
Sherman: Organic Analysis; Rolfe: The Polariscope in the 
Laboratory. 

MILK. 

General Statements. — Milk is an emulsion of fat-globules 
with casein and other nitrogenous bodies, mineral salts 
(probably in combination), sugar and water. The average 
percentage composition of the more important varieties of 
milk, as found by recent observers, is summarized in the fol- 
lowing table: 

Water. Sugar. Proteids. Fat. Ash. 

Cow 86.90 4.80 3.60 4.00 O.70 

Human 88.75 6.00 1.50 3.45 0.30 

Goat 85.70 4.45 4.30 '4-75 0.80 

Ass 89.50 6.25 2.00 1.75 0.50 

Mare 90.75 5-70 2.00 1.20 0.35 

Sheep 80.80 4.90 6.55 6.85 0.90 

In connection with this table should be noticed the high 
proportion of sugar and low proportion of casein and ash in 
human milk as compared with cow's milk. The former is not 
readily curdled, the casein never separating in a compact clot 
which settles to the bottom, a difference which is attributed 
to the lower proportion of fat to casein.* 

The average composition of 14,967 samples of cow's milk 

* Lehmann and Hempel: Arch. Physiol., 56 (1894), 558. 



food: analytical methods: milk. 169 

for the year 1907, analyzed directly on arrival of the milk from 
the farm, is given by Richmond * as follows: 

Average, 1907. 

Specific gravity 1 .0322 

Total solids 1 2 . 69 

Solids not fat 8 . 94 

F ^ 3-75 

The U. S. standard for whole milk requires that it shall 
contain not less than 8.5 per cent of solids not fat, and not 
less than 3.25 per cent of milk fat.j 

From the average values there are constant variations, due 
to the time of milking, the season of the year and the breed and 
feed of the cow. The proportion of milk sugar and ash is most 
nearly constant, while the fat is the most variable constituent. 

An examination of milk as regards its health fulness usually 
consists in determining what changes, if any, have taken place 
in its constituents due to the growth of micro-organisms. 
Milk is a natural culture medium for the growth of micro- 
organisms and they increase in it with almost incredible 
rapidity. These changes which take place are called " fer- 
mentations." The two most common are the acid and the 
alkaline. 

Acid Fermentation. — Milk-sugar is converted wholly or in 
part into lactic acid under the influence of a class of organisms 
of which bacillus acidi lactici is the best known and is generally 
regarded as predominating. The extent to which this change 
has taken place is shown by the test for acidity. 

Alkaline Fermentation. — In the alkaline fermentation the 
albumin and casein are decomposed with the formation of 
ammonia and other intermediate nitrogenous products, some 
of them of a poisonous character, as is shown by the preval- 
ence of cholera infantum when such decomposed milk is used, 

* Analyst, 1908. 

| Circular No. 19, Office of the Secretary, U. S. Dept. Agriculture. 



170 AIR, WATER, AND FOOD. 

and by cases of poisoning by ice-cream, etc. This fermenta- 
tion generally occurs simultaneously with the acid fermen- 
tation, but at first is much less active; at a subsequent stage, 
however, the alkaline fermentation becomes more pro- 
nounced, and in certain cases may completely dominate the 
other fermentations. 

Other Fermentations. — Butyric acid fermentation may be 
a result of the action of one or several groups of bacteria upon 
the glyceride of butyric acid. This action sets free the butyric 
acid in part and the fat becomes in time " rancid," but this 
change takes place, as a rule, more slowly and is not so com- 
mon as the others. 

The production of koumiss is an instance of an artificially 
incited change. Various other fermentations occasionally 
occur which cause a slimy appearance or a bitter taste. 
Various colors may be imparted to the milk by the presence 
of chromogenic or color-producing micro-organisms. The 
student is referred to the various journals and to text-books 
on dairy bacteriology for accounts of these less important 
changes. 

Sampling. — In all manipulations with milk the importance 
of thorough and frequent mixing, not shaking, cannot be too 
strongly emphasized; this is best accomplished by pouring it 
from one vessel to another. This will be found necessary 
even when the milk has been standing for only a few minutes, 
on account of the rapid rise of the cream. The apparatus 
used to contain or to measure milk should be thoroughly 
washed out as soon as possible. 

PHYSICAL TESTS. 

Specific Gravity. — Take the specific gravity in the usual 
manner by means of a hydrometer at i5°.6 C. If the temper- 
ature of the milk varies only a few degrees from this, the read- 
ing may be corrected by means of Table IX, Appendix A. 



food: analytical methods: milk. 171 

Hydrometers for special use with milk are known as lac- 
tometers and are usually so graduated as to read in degrees 
corresponding to the gravity. Thus in the Quevenne lactometer, 
the graduation from 15 ° to 40 corresponds to a specific gravity 
1. 015 to 1.040. 

The New York Board of Health lactometer has an arbitrary 
scale, reading zero in pure water and 100 in " pure milk," which 
is taken as corresponding to a specific gravity of 1.029. From 
the scale-reading the specific gravity may readily be calculated. 

Notes. — The specific gravity of milk is, in the main, a func- 
tion of two factors, namely, the percentage of solids not fat 
and of the fat. The former raises it; the latter lowers it. The 
determination of the specific gravity alone is not to be relied 
upon as an absolute index of the purity of the milk. The 
specific gravity varies in general from 1.029 to 1.034, and in 
most cases of normal and well-mixed milk from several cows 
the specific gravity will lie between 1.030 and 1.032. 

Opacity. — The white color and opacity of milk are 
largely due to the presence of the suspended fat-globules and 
of the casein in colloidal form. The influence of the latter is 
shown by the fact that the color of milk is not greatly 
changed after it has passed through a centrifugal separator 
which removes practically all of the fat. The degree of 
opacity and the percentage of fat may be determined by 
means of Feser's lactoscope, the modus operandi of which is 
given with that instrument. Another instrument of like prin- 
ciple is Heeren's pioscope,* which consists of an ebonite disk 
with a raised rim; a drop or two of milk is placed upon it, the 
painted glass cover placed over it, and the color of the milk 
matched with one of those on the cover. 

Cream. — Fill the creamometer, an elongated test-tube 
with graduations near the top, to the zero mark with the 

*Repit.f. Anal. Chem., 1881, 247, 



I7 2 AIR, WATER, AND FOOD. 

milk, add three drops of a solution of methyl violet, mix and 
put away in a cold place. After twenty-four hours read off 
the percentage of cream. 

Notes. — The rapidity with which the cream rises indicates 
whether sodium carbonate has been added, its action being 
to retard the rise of cream so that the milk is never blue. 
Should the cream separate very quickly and the milk be blue, 
the indication is that water has been added or that the milk 
is of poor quality. The method is only approximate and does 
not give the amount of fat. The methyl violet is added to 
render the reading sharper, as it does not dissolve appreciably 
in the cream. Cream contains most of the fat of milk with a 
small proportion of the other constituents, ioio samples of 
cream gave an average of 48.3 per cent. fat. 

CHEMICAL TESTS. 

Reaction. — Normal milk gives the amphoteric reaction, 
that is, it turns delicate litmus both red and blue. This is due 
to the presence of neutral and acid phosphates of the alkalies. 
The reaction of the milk soon becomes acid, however. 

Acidity. — Measure 5 c.c. of milk into a small beaker, 

N 
dilute with so c.c. of water, and titrate the acid with — 
J 10 

sodium hydroxide, using phenolphthalein as an indicator. 
Express the acidity in degrees, considering each tenth of a 
cubic centimeter of sodium hydroxide one degree. 

Notes. — The acidity of milk is due to the fermentation of 
milk-sugar and the production of lactic acid. Under favor- 
able circumstances this change may take place with consid- 
erable rapidity. For example, six hours after milking the 
acidity may be fourteen to twenty-five degrees; forty-eight 
hours after milking it may reach one hundred degrees. When 
the acidity reaches twenty-three degrees milk coagulates on 



food: analytical methods: milk. 173 

boiling.* An example of the rate of change is given in the 
following table :f 

n Acidity, Sugar, 

uay - c.c. Degrees of Rotation. 

1 2.2 25.2 

2 5.5 23.I 

3 II. O 21.6 

6 13.2 I4.2 

7 i5-o 9-4 

8 16.3 7.8 

9 17.2 1.2 

Total Solids. — The determination of total solids is best 
carried out in a platinum dish having a flat bottom about 2\ 
inches in diameter. Small dishes of aluminum or lead foil, or 
blacking-box covers answer very well, but of course cannot be 
ignited to obtain the ash. 

Directions. — Weigh the platinum dish and add about 5.1 
grams to the weights on the balance-pan. With the burette 
pipette deliver 5 c.c. of the well-mixed milk into the dish and 
weigh the whole as rapidly as possible to the nearest milli- 
gram. Evaporate the milk to dryness on the water-bath and 
then dry it in the oven at ioo° to constant weight. 

Notes. — It is important that the milk should be in the form 
of a thin layer, so that the evaporation of the water shall take 
place as quickly as possible. Under these conditions the resi- 
due obtained is nearly white; but if the process be prolonged, 
it may have a brownish color from the caramelization of the 
sugar. 

Various analysts have proposed modifications of the pro- 
cedure as described above, such as drying on sand or asbestos , 
coagulation of the milk by absolute alcohol before evaporation, 
and so forth, but simple evaporation in an open dish is generally 
regarded as the most advantageous. 

Ash. — Directions. — Ignite the platinum dish containing 
the residue from the preceding determination at a low red 

* Thorner: Analyst, 16 {1891), 200. 

t " Thesis," Ethel B. Blackwell, M.I.T., 1891. 



174 AIR j WATER, AND FOOD. 

heat until the ash is white or nearly so. This may be done 
over a burner carefully regulated so that the dish is nowhere 
heated above a dull redness, or in a muffle furnace. After 
weighing the ash, test it for carbonates by adding two drops 
of dilute hydrochloric acid. Effervescence in the ash is quite 
perceptible when carbonates are present in as small amount 
as 0.05 per cent. If desired, the hydrochloric acid solution of 
the ash can be used to test for boric acid as described on page 
188. 

Notes. — If the temperature is raised too much during ignition, 
the results will be low on account of the partial volatilization 
of the chlorides of the milk; hence the process should be 
carried out at as low a temperature as will admit of the oxida- 
tion of the carbonaceous matter. 

The percentage composition of the ash of milk is given 
by Fleischmann and Schrodt * as follows: 

Per cent. 

Potassium oxide, K 2 25.42 

Sodium " Na 2 10.94 

Calcium " CaO 21.45 

Magnesium " MgO 2.54 

Ferric " Fe 2 3 0.11 

Sulphuric acid, S0 3 4.11 

Phosphoric " P 2 5 24.11 

Chlorine, CI 14.60 

103.28 
Less oxygen corresponding to chlorine f 3.28 

100.00 

The ash of genuine cow's milk is free from carbonates and 
borates, and the ash soluble in water is about 30 per cent, of 
the total. The ash determined in this way does not represent 
exactly the mineral salts present in the milk, since these are 
altered by the oxidation to some extent. 

*Baumeister: "Milch und Molkerei-Producte." S. 16. 

f This correction is necessary because the metals are all calculated as 
oxides, when, as a matter of fact, a certain proportion are present as 
chlorides. 



food: analytical methods: milk. 



/:> 



Fat. — Since the fat is so important a constituent of milk, 
an endless variety of methods and modifications for its deter- 
mination have been devised. The processes which are in 
most general use may be divided into three classes: 

i. Estimation of the fat by simple extraction of the milk, 
best dried on some absorbent material. 

2. Volumetric estimation of the fat liberated by chemical 
treatment from the milk and collected by centrifugal force. 

3. Estimation of the fat by extraction from the milk itself 
after solution of the casein by acid. 

A typical method from each class will be described in de- 
tail. 

(t) Adams' Method. — Directions. — Roll a strip of fat- 
free blotting-paper, 22 inches long and 2-J inches wide, into 
a rather loose coil and fasten it by a bit of copper wire. Hold 
the coil in one hand and carefully run on to the upper end of 
it 5 c.c. of milk from a burette pipette. Place the coil, diy 
end downward, in the water-oven and dry it for an hour. 
When dry remove the wire and place the coil in the Soxhlet 
extractor. If preferred, the strip of paper may be held hori- 
zontally in a frame and the milk run on to it. When dry the 
paper is rolled into a coil and extracted. Weigh the extraction- 
flask, place in it 75 to 100 c.c. of petroleum ether and connect 
the extractor with the condenser. After the coil has been 
extracted for at least two hours remove the extractor and 
evaporate the petroleum ether at low temperature, taking care 
to avoid the vicinity of free flames. Dry the flask with the 
extracted fat in the water oven to constant weight. Avoid pro- 
tracted heating, which would cause partial oxidation of the fat. 

Notes. — Absorbent paper exercises a selective action on 
the constituents of milk so that the fat is left on the surface of 
the paper, mixed with only about one-third of the non-fatty 
solids, and hence it is more easily extracted; further, owing 
to the greatly increased surface exposed, the extraction of the 
fat is practically complete. 



176 



AIR, WATER, AND FOOD. 



Ethyl ether may be used instead of petroleum ether, but care 
should be taken that the ether is perfectly dry, otherwise other 
substances than fat, principally milk-sugar, will be extracted. 
On the other hand, substituted glycerides may not be dissolved 
out by ether. For these reasons the petroleum ether is to be 
preferred as a solvent, although its action is considerably 
slower than that of the other. 

Owing to the inflammable nature of the solvents employed, 




Fig. 12. — Apparatus for Fat Extraction. 

it is best not to use a flame as the source of heat, but to heat 
the flask by means of a steam- or water-bath. In this labora- 
tory small electric heaters about 4 inches in diameter are used 
and have been found safe and convenient. The complete 
apparatus is shown in Fig. 12. In using these it should be 
borne in mind that considerable quantities of ether or petroleum 
ether in contact with the heatea surface may ignite, and caution 
should be taken not to evaporate any quantity of these solvents 
from an open vessel. 

(2) Babcock Method. — Directions. — Measure 17.6 ex. of 
the milk from a pipette into the long-necked, graduated whirling- 



food: analytical methods. 177 

bottle. Measure out 17.5 c.c. of sulphuric acid 1^0, gr. 1.83 ) r 
and add it gradually to the milk, mixing the t\*-« thoroughly 
after each addition. Take care that none of the liquid spurts 
into the neck of the bottle. After mixing the milk and acid, 
and while the bottles are still hot, place them in opposite 
pockets in the centrifugal machine, in even numbers, and 
whirl them for five minutes, at full speed. Then remove the 
bottles and add hot water up to the necks, after which whirl 
them again for one minute. Again add hot water until the 
fat rises to the 8 mark on the stem. Place the bottles in the 
machine and whirl them at the same rate as before for one 
minute. Then measure the length of the column of fat by a 
pair of dividers, the points being placed at the extreme limits 
of the column, the fat being kept warm, if necessary, by standing 
the bottle in hot water. If now one point of the dividers is 
placed at the zero mark of the scale on the bottle used, the other 
will indicate the per cent, of fat in the milk. 

Notes. — When the acid and milk are mixed the mixture 
becomes hot from the action of the acid on the water in the 
milk and turns dark-colored on account of the charring of 
the milk-sugar. The casein is first precipitated and then 
dissolved. The fat is thus separated in a pure state from the 
other constituents of the milk. 

The fat obtained should be of a clear, golden-yellow color, 
and distinctly separated from the acid solution beneath it. 
If the fat is light-colored or whitish, it generally indicates that 
the acid is too weak, and a dark-colored fat with a stratum 
of black particles below it indicates that the acid is too strong. 
The best results will be obtained by the use of acid of the 
strength noted above. 

A violet color is sometimes produced when the first por- 
tions of the acid and milk are mixed. This frequently indi- 
cates the presence of formaldehyde. (See p. 187.) 



1 7 8 



AIR, WATER, AND FOOD. 



(3) Gottlieb Method. — Directions. — Measure 5 c.c. of milk 
into a glass-stoppered 50-c.c. cylinder and add the following 
reagents, being careful to add them in the order given and to 
shake the stoppered cylinder thoroughly after the addition of 
each reagent: 1 c.c. of ammonia, sp. gr. 0.96, 5 c.c. of alcohol, 
12.5 c.c. of ethyl ether and 12.5 c.c. of petroleum ether. Let 
the cylinder stand until the lower layer is free from bubbles, 
over night if necessary. 

With ordinary milk the separation takes place rapidly, but 
with sweetened condensed milk the longer time may be necessary. 
Transfer the upper layer to a tared flask by means of the 
apparatus shown in Fig. 13. This consists of a cork carrying 
an ordinary glass T tube. Through the straight 
limb of the T tube slides a bent glass tube, 
which is turned up at the lower end. The tube 
is adjusted by sliding it through the rubber 
collar (C) so that the lower end rests just above 
the junction of the two layers. On then blow- 
ing gently in the side arm (5), the upper layer 
is forced out into the flask. Repeat the extrac- 
tion once, using 10 c.c. each of ether and pe- 
troleum ether and blowing it off into the flask. 
Distil off the solvent and dry the residual fat 
to constant weight in the water oven. 

Notes. — It is almost useless to try to extract 
the fat from milk by shaking it directly with 
.a solvent. An emulsion is formed with the other constituents 
of the milk, and it is impossible to get a good separation of 
the solvent even with the centrifugal machine. This is prob- 
ably due to the action of the colloidal casein, because it is 
found that when a complete or partial solution of the casein 
is effected it is comparatively easy to extract and separate 
the fat by a solvent immiscible with water. 




food: analytical methods: milk. 179 

The method is applicable to whole milk but is especially 
valuable in determining fat in such products as skim milk or 
butter milk, which are low in fat. It is also of value in the 
analysis of sweetened condensed milk. 

Relation between Specific Gravity, Fat, and Solids 
in Milk. — As has been stated already, the specific gravity 
of milk is, in the main, a function of two factors, namely, 
the percentage of solids not fat and that of the fat. The former 
raises it, the latter lowers it. Taken by itself it affords very 
little indication of the composition, but if any other item be 
known, it should be possible to find, by calculation, the other 
quantities, provided the assumption is true. The solids not 
fat are made up of several fluctuating constituents, but " nor- 
mal milk " seems to contain them in such a constant ratio 
that a calculation serves at least to detect an abnormal sam- 
ple. For example, given the specific gravity and solids to 
calculate the fat: 

Specific gravity = Gr. The amount which each per cent, 
of solids not fat raises the specific gravity = s. The amount 
which each per cent, of fat lowers the specific gravity = f. 
Total solids = T. Solids not fat = 5\ Fat = F. Gr = Ss 
— Ff; or, substituting for 5 its value T — F; Gr = (T — F) 
s — Ff. The uncertainty of the calculation lies in the val- 
ues of s and f, which have not been quite satisfactorily deter- 
mined. 

At different times various formulae have been proposed 
for this calculation, varying, as a matter of course, with 
tha method of fat extraction employed. The one most 
extensively used is that of Hehner and Richmond,* which 
is based on extensive observation and perfected process 

* Analyst, 13 {1888), 26; 17 (1892), 170. 



i8o 



of fat extraction. This formula is generally stated as fol- 
lows: 

F = 0.8597 — 0.2186G, 

where F represents the fat, 7"the total solids, and G 1000 X 
(specific gravity — 1.000). 

The simple formula —F = T — — answers within the 
F 5 4 

limits of experimental error for normal milk, but not for 
skimmed or watered milk. 

Example. — Data: Gr = 1.0323; G = (Gr — 1) X 1000 = 
32.3; T= 12.90. 

6 32. ^ 

—F= 12.90 — . F — 4.02 calculated, 3.99 found. 

A similar relation has been worked out for the poteids 
and sugar, so that from three determinations the whole com- 
position may be calculated. Example as above: 

Ash = .70 = A. 

Q 

Formula: P= 2.ST + 2.$A — 3.33F — .68—-, 

Gr. 

or P=z 36.12 + 1.75 — 13.32 — 21.28 = 3.27. 

Sugar = T-{A + P+F) 

= I2.90 - (.70 + 3.27 + 4.02) z= 4.9I. 

Where a number of calculations are to be ma^e, Rich- 
mond's milk-scale will be found convenient. This is an in- 
strument based on the principle of the slide-rule, having three 
scales, two of which, for the fat and the tota 1 solids, are 
marked on the body of the rule, while that for the spe ific 
gravity is marked on the sliding part. Extended tables are 
also used for the same purpose. 



Analyst, 13 {1888), 26; 17 {i8g2), 170. 



food: analytical methods: milk. 181 

Milk-sugar. — The methods for the determination of the 
sugar in milk may be divided into two general classes: (i) 
those depending on the reducing power of the sugar upon an 
alkaline copper solution; (2) those which are based upon 
observations of the degree of rotation of the plane of polarized 
light. 

(1) Determination by Fehling's Solution according to 
Munson and Walker.* 

Directions. — The milk must first be clarified to remove 
substances other than sugar which would exert a reducing 
action on the Fehling's solution. 

Measure 25 c.c. of milk into a 500-c.c. calibrated flask. Add 

about 400 c.c. of water, 10 c.c. of Fehling's copper sulphate 

N 
solution, then 35 c.c. of — NaOH, and make up to 500 c.c. 

Mix thoroughly and filter through a dry filter. 

Determination. — In a No. 3 beaker mix 25 c.c. of the Fehling's 
copper sulphate solution and 25 c.c. of the alkaline tartrate 
solution. Add 50 c.c. of the milk sugar solution, prepared as 
above, cover the beaker with a watch glass, and heat it upon 
wire gauze. Regulate the flame so that boiling shall begin in 
four minutes, and continue the boiling for exactly two minutes. 

Filter the cuprous oxide without delay through asbestos in 
a weighed Gooch crucible, wash it with hot water until free 
from alkali, pour out the hot nitrate, then wash with 10 c.c. 
of alcohol and finally with 10 c.c. of ether. Dry the crucible 
for 30 minutes at the temperature of boiling water and weigh. 
Find the milligrams of lactose monohydrate corresponding to 
the weight of cuprous oxide from Table XII on page 248 and 
•calculate the percentage present in the milk. 

* J. Am. Chem. Soc. (1906), 663; (1907), 541. 



l82 AIR, WATER, AND FOOD. 

Notes. — The general principle upon which all these methods 
depend is based on the fact that certain sugars, among which 
is lactose, have the power of reducing an alkaline solution of 
copper to a lower state of oxidation in which copper is separated 
as cuprous oxide. The copper salt which is found to give the 
most delicate and reliable reaction is the tartrate. The two 
solutions which make up the Fehling's solution are best preserved 
separately, and rrixed only when wanted for use, as otherwise 
the reducing power of the solution is liable to change. 

The amount of reduction of the copper salt to the cuprous 
oxide is affected by the rate at which the sugar solution is 
added, the time and degree of heating, and the strength of 
the sugar solution; hence the necessity for adopting a definite 
procedure and for taking the results from a table determined 
by exactly the same procedure for varying amounts of the 
sugar. 

The asbestos which is used should be previously boiled in 
nitric acid and then in dilute sodium hydroxide and thoroughly 
washed. A layer about a centimeter thick should be used in 
the crucible, and a " blank " determination made with the 
Fehling's solution should not show a change in weight greater 
than one-half milligram. After the precipitated cuprous oxid: 
has been weighed it may be dissolved in hot dilute nitric acid, 
the asbestos in the crucible washed and dried as described, 
when it is again ready for use. Do not remove the asbestos 
from the crucible. 

(2) Determination by the Saccharimeter. — For the 
optical determination of milk-sugar the method of double di- 
lution, as described by Wiley and Ewell,* will be found satis- 
factory. 

Directions. — Into each of two flasks, marked at 100 and 
200 c.c, respectively, put 65.52 grams of milk, add 10 c.c. of 
acid mercuric nitrate, fill to the mark, and mix by shaking. 

* Analyst, 21 (ySg6), 182. 



food: analytical methods: milk. 183, 

Filter through dry filters and polarize in a 400-millimeter 
tube, using the Schmidt and Haensch saccharimeter. Cal- 
culate the results as in the following example: 

Weight of milk used = 65.52 grams; 

Reading from 100-c.c. flask = 2o°.84; 
" " 200-c.c. flask = io°. 15. 

Then 10. 15 X 2 = 20.30; 

20.84 — 20.30 = 0.54; 
0.54 X 2 = 1.08; 

20.84 — 1.08 = 19.76; 
19.76 —■ 4 = 4.94, which is the per cent- 

of milk-sugar. 

Notes. — The object in using the method of double dilu- 
tion is to avoid the necessity of making corrections for the 
volume of the precipitate of casein and fat. The method is 
based on the fact that, within certain limits, the polarizations 
of two solutions of the same substance are inversely propor- 
tional to their volumes. 

The flasks should be filled at nearly the same temperature 
as that at which the polarizations are made, and the tem- 
perature of the room should be kept as nearly as possible 
at 20 to avoid errors arising from marked changes in tem- 
perature. 

PROTEIDS OF MILK. 

Determination of Total Proteids. — Weigh 5 grams of 
milk into a digestion flask and determine the nitrogen by the 
Kjeldahl process, as directed on page 206. Multiply the per 
cent, of nitrogen by the factor 6.38 to obtain the per cent, of 
proteids. The frothing of the alkaline solution during the 
distillation may be prevented by the addition of a piece of 
paraffin about the size of a bean. 



184 AIR, WATER, AND FOOD. 

Determination of Casein and Albumin.* — Directions. — 
To 10 grams of milk add 90 c.c. of water at 40-42 C. and 
then 1.5 c.c. of 10 per cent, acetic acid. Agitate and warm 
at the above temperature until a flocculent precipitate sepa- 
rates, leaving a clear supernatant liquid. Filter, wash, and 
determine the nitrogen in the washed precipitate and filter by 
the Kjeldahl process. Multiply by 6.38 for the casein. 

To determine the albumin neutralize the filtrate with 
caustic alkali and phenolphthalein and heat it at ioo° C. until 
the precipitate settles clear. Filter, wash, and determine the 
nitrogen as before. Nitrogen multiplied by 6.38 equals albumin. 

Notes. — The principal proteid bodies present in milk are 
casein and albumin. Others are present in much smaller 
quantity, such as fibrin or globulin. 

Different observers at various times have claimed the 
presence of other nitrogenous bodies, but these have not been 
entirely substantiated. 

It is now generally held that the colloidal state in which the 
casein is held in milk is due to the combination with it of certain 
mineral compounds, chiefly those of calcium. The action of 
precipitants is on these mineral matters, breaking up the com- 
bination and releasing the insoluble casein. 

Interpretation of Results. — The most common forms of 
adulteration of milk are the addition of water and the removal 
of cream. Occasionally some foreign material may be added. 
A good idea of the form of adulteration may usually be gained 
from the relation between the fat and the solids not fat. In 
watered milk both of these are low, but the ratio between them 
is about the same as in normal milk. In skimmed milk the 
solids not fat may be nearly normal while the fat is very low. 
If the total solids and the solids not fat are both below standard, 

* Van Slyke and Hart: Am. Chem. J., 29 (1903), 170. 



food: analytical methods: milk. 185 

while the proportion of fat to solids not fat is very small, it is 
a fair assumption that the milk is both skimmed and watered. 

Leach * states that it is nearly always safe to condemn a 
milk as watered, if the total solids are below 10.75 per cent., 
with a corresponding amount of fat. 

Direct Determination of Added Water. — This may be done 
by determining the specific gravity of the milk-serum after 
coagulation and removal of the casein. f The casein is coag- 
ulated by dilute acetic acid, filtered off on a dry filter, and 
the specific gravity of the nitrate taken at 15 C. by the West- 
phal balance. The specific gravity of the serum from normal 
milk is never below 1.027, an( ^ oruv rarely below 1.029. The 
addition of each ten per cent, of water lowers tne specific 
gravity by 0.0010 to 0.0035. 

A more convenient method of determination is Dy the Zeiss 
immersion refract ometer if this instrument is available. (See 
Bur. of Chem., Bui. 107 (Revised), p. 120; also 1-eacn, Food 
Inspection and Analysis, p. 766.) The Abbe reiractometer, 
page 202, can also be used. 

The determination is often of importance since it enables 
the analyst to distinguish readily between milk which is directly 
adulterated on the one hand, and that which is only below 
standard on the other. In legal prosecutions the amount of 
penalty imposed is sometimes dependant on whether the analyst 
can show evidence of the actual addition of water. 

Cane-sugar. — To detect the presence of cane-sugar boil 
about 10 c.c. of the milk with 0.1 gram of resorcin and 1 c.c. 
of rrydrochloric acid for five minutes. The liquid will be 
colored rose-red if cane-sugar be present. The quantitative 
determination may be made by means of the polariscope. 

* "Food Inspection and Analysis." 

f Woodman: J. Am. Chem. Soc, 21 (1899), 503; Leach: "Food Inspection 
and Analysis," p. 765. 



l86 AIR, WATER, AND FOOD. 

Cane sugar is occasionally found in the milk through the use 
of diluted condensed milk to eke out the supply. 

Starch. — Heat 10 c.c. of the milk to boiling in a test-tube, 
and when cold add a few drops of the solution of iodine in 
potassium iodide. The presence of even 0.2 per cent, of starch 
will be shown by the characteristic blue coloration. 

Coloring-matters. — The principal coloring-matters added 
to milk are annatto, caramel, and coal-tar dyes. In general, 
coloring-matters are added only to watered milk, but 
general, coloring-matters are added only to watered milk, but 
occasionally samples which were of standard quality have 
been found to be colored. 

Directions .—Put about 100 c.c. of the milk into a small 
beaker, add 2 c.c. of 25 per cent, acetic acid and allow the 
beaker to stand quietly for about ten or fifteen minutes in 
a water-bath kept at 70 C, the casein being thus separated 
as a compact cake. Decant off the whey, squeezing the 
curd as free from it as possible by means of a spatula. Trans- 
fer the curd to a flask and let it remain covered with ether 
for an hour or more. 

Evaporate the ether extract, which contains the annatto 
if present, add 5 c.c. of water, and dilute sodium hydroxide 
until the mixture, after thorough beating and stirring with 
a glass rod is faintly alkaline to litmus paper, and filter 
through a wet filter. If annatto is present, it will permeate 
the filter and give it an orange color when the fat is washed 
off under the tap. Treat the filter with stannous chloride. 
If annatto is present, a pink color will be produced. 

After pouring off the ether examine the milk-curd for 
caramel or aniline orange. If the curd is left white, neither 
of these colors is present. If caramel has been used, the 
curd will be of a pinkish-brown color; if the color is due to 
the aniline dye, the curd will have a yellow or orange tint 
In doubtful cases the curd should be compared with one from a 



food: analytical methods: milk. 187 

milk known to be uncolored. To distinguish between the two 
colors shake a small portion of the curd in a test-tube with 
strong hydrochloric acid. The caramel-colored curd will act 
similarly to an uncolored curd, that is, it will gradually produce 
a deep blue color in the solution. On the other hand, the 
coal-tar color will immediately produce with the hydrochloric 
acid a pink color. 

Note. — It is to be regretted that there is no positive test 
for caramel sufficiently delicate to serve here. The test as 
described is a negative one, the only indication of caramel being 
the occurrence of a colored curd in which the color is not given 
by the coal-tar dye. 

Preservatives. — The preservatives usually added to milk 
are formaldehyde and borax or boric acid. Carbonate of soda 
is added in some cases to disguise the acidity of sour milk. 

Formaldehyde. — This is generally used as a 40 per cent, 
aqueous solution, sold under the name of formalin. Several 
simple tests commonly used for the detection of formaldehyde 
will be described. 

(1) When the sulphuric acid is added to the milk in making 
the Babcock test for fat, a bluish- violet ring will be noticed 
at the junction of the two liquids when formaldehyde is present. 
One part of formaldehyde in 200,000 parts of milk can be 
detected by this test, but it fails when the formaldehyde amounts 
to 0.5 per cent. The test is more delicate if the sulphuric acid 
contains a trace of ferric chloride. 

(2) To 10 ex. of milk in a small porcelain dish add an equal 
volume of hydrochloric acid (1.20 sp. gr.). Add one drop 
of ferric chloride solution and heat the dish with a small flame, 
stirring vigorously, until the contents are nearly boiling. 
Remove the flame and continue the stirring for two or three 
minutes, then add about 50 c.c. of water. The presence of 
formaldehyde will be shown by a violet color which appears in 



i88 

the particles of the precipitated casein, the depth of color 
depending on the amount of formaldehyde present. The color 
should be observed carefully at the moment of dilution. This 
test readily shows the presence of one part of formaldehyde in 
250,000 parts of milk, if fresh. 

Boric Acid or Borax. — Make 25 c.c. of the milk distinctly 
alkaline with lime water and evaporate to dryness on the 
water bath. Char the residue over a flame but do not neces- 
sarily heat it until white. Digest the residue with 15-20 c.c. 
of water and add hydrochloric acid (1.12) until the mixture 
is faintly acid to litmus paper. Filter, and add 1 c.c. of acid 
fn excess. Place a strip of turmeric paper in the solution and 
evaporate to dryness on the water bath. If boric acid or borates 
are present, the paper takes on a peculiar red color, which is 
changed by ammonia to a dark blue-green, but is restored by 
acid. Excess of hydrochloric acid should be avoided, as it 
turns the paper a dirty green when evaporated. This test 
can also be applied to the hydrochloric acid solution of the ash. 

Sodium Carbonate. — Detected in the milk-ash, as on page 
174. If effervescence occurs, test the original milk with rosolic 
acid as follows: Mix 10 c.c. of milk with an equal volume of 
alcohol, and add a few drops of a one per cent, solution of 
rosolic acid. The presence of sodium carbonate is indicated 
by a more or less distinct pink coloration. A comparative 
test should be made at the same time with milk known to be 
pure. 

CONDENSED MILK. 

. It may in some cases afford an interesting variation to 
carry out the tests on condensed milk, this having within recent 
years become an important article of food. With the unsweet- 
ened condensed milk, commonly sold as " evaporated milk," 
the methods as used with whole milk can be applied directly to 



food: analytical methods: milk. 



189 



the diluted sample. In the case of sweetened condensed milk, 
which is usually meant by the term condensed milk in this 
country, the methods must in some cases be modified, on 
account of the large proportion of cane sugar present. 

The following are analyses of a few typical samples of 
sweetened condensed milk: 



COMPOSITION OF SWEETENED CONDENSED MILK. 





















Degree 

of 
Con- 
densa- 
tion. 


Fat in 




Total 
Solids. 


Water. 


Milk 
Solids. 


Cane- 
sugar. 


Lac- 
tose. 


Pro- 
tein. 


Fat. 


Ash. 


Origi- 
nal 
MUk. 


I 1 


72.95 


27.05 


30.01 


42.94 


11.28 


7-85 


9-3 


1.58 


2.26 


4. II 


2 2 


71 .03 


28.97 


27.49 


43-45 


11.78 


7-51 


6.6 


1.60 


2.29 


2.88 


3 J 


7i-5« 


28.42 


24.24 


47-34 


13.08 


9.04 


0.15 


1.97 


2.8 


0.05 



Normal. 



2 Not made from standard milk. 



3 Condensed from skimmed milk. 



Preparation of the Sample. — Transfer the entire contents of 
the can to a large evaporating dish, scraping it out clean, and 
work it thoroughly with a pestle until homogeneous. Weigh 
out 40 grams of the mixed sample and dilute to 100 c.c. in a 
calibrated flask. 

Total Solids. — Dilute 10 c.c. of the 40 per cent, solution with 
an equal volume of water and evaporate 5 c.c. of the diluted 
mixture, corresponding to 1 gram of the sample, to dryness in 
a weighed platinum dish, as directed on page 173. It is of 
importance to have the sample very dilute in order to get an 
accurate determination of the solids and this can best be 
accomplished in the manner described. 

Ash. — Ignite the residue from the determination of total 
solids, as in the case of ordinary milk. 

Fat. — The fat is the determination of most importance since 
judgment of the quality of the sample is based more largely on 
this factor than on any other. Its determination, however, is 



190 AIR, WATER, AND FOOD. 

attended with some difficulty on account of the large amount of 
cane sugar present. The Babcock method, for instance, does 
not give satisfaction since the charring of the sugar by the 
sulphuric acid prevents a clean separation of the fat. The 
Adams method, moreover, is unreliable because the cane sugar 
dries on the paper coil, enclosing the fat so that it is not readily 
extracted by the solvent. Several modifications of these 
methods have been proposed, however, by which fairly good 
results may be obtained. 

Babcock Method as modified by Leach. — Leach has modified 
the Babcock test so as to make it available for sweetened con- 
densed milk by precipitating the proteids and fat with copper 
sulphate and then removing the interfering sugar by several 
extractions with water. Directions for carrying out the test 
will be found in Leach: Food Inspection and Analysis, p. 149, 
or in Bur. of Chem., Bui. 107, p. 123. 

Adams Method. — This can be applied in the following 
manner: Dry 5 c.c. of the 40 per cent, solution on the paper 
coil, as described on page 175. Extract with petroleum ether 
in the usual manner; dry, soak the coil in 500 c.c. of water for 
several hours; dry, extract again for five hours and weigh the 
fat as usual. 

Gottlieb Method. — Use 10 c.c. of the 40 per cent, solution 
and carry out the determination exactly as described on page 
178. In many ways this method will be found to give the best 
results on condensed milk. 

Proteids. — Determine nitrogen in 5 c.c. of the 40 per cent, 
solution and multiply by 6.38. 

Lactose. — Use the method described on page 181 on 25 c.c. 
of the 40 per cent, solution. 

Cane Sugar.— This may be determined with sufficient 
accuracy for most purposes by difference, subtracting the milk 
solids (the sum of the lactose, fat, protein and ash), from the 



food: analytical methods: milk. 191 

total solids. The direct estimation of the cane sugar in the 
presence of lactose may be carried out with the polariscope 
by the choice of a suitable inverting agent. The writer has 
obtained good results by inversion with acid mercuric nitrate, 
as described by Harrison.* 

BUTTER. 

General Statements .—Butter consists of the fat of milk, 
together with a small percentage of water, salt, and curd. 
The curd is made up principally of the casein of the milk. 
These various ingredients are present in about the following 
proportions : 

Fat 78.00-90.0 per cent. ; average, 82 per cent. 

Water 5.00-20.0 " " " 12 " " 

Salt 0.40-15.0 " " " 5 " " 

Curd 0.11- 5.3 " " " 1 " 

The fat consists of a mixture of the glycerides of the 
fatty acids. The characteristic feature of butter-fat is the 
extraordinarily high proportion of the glycerides of the solu- 
ble and volatile fatty acids when contrasted with other fats. 

Tl e following may be taken as the probable composition 
of normal butter-fat: 

Acid. Per cent. Acid. Per cent. Triglycerides. 

Dioxystearic 1 .00 1 .04 

Oleic 32.50 33.95 

Stearic 1.83 1.91 

Palmitic 38.61 40.5 1 

Myristic 9.89 10.44 

Laurie 2.57 2.73 

Capric 0.32 0.34 

Caprylic 0.49 0.53 

Caproic 2.09 2.32 

Butyric 5.45 6.23 

Total 94-75 100.00 

Accordiug to this, the proportion of volatile acids in butter 
(butyric, caproic, caprylic, and capric acids) amounts to 8.35%. 
The amount of volatile acid in lard, for example, is about 0.1%. 

"■Analyst, 29, 248. f Browne, /. Am. Chem. Soc, 21 (1899), 807. 



192 AIR, WATER, AND FOOD. 

The usual examination of butter consists in the examina- 
tion of the butter-fat, in order to detect the presence of 
foreign fats. The determination of the amount of curd may 
be of value also in some cases, more especially from a 
sanitary standpoint. The chief danger to health probably 
lies in the possible decomposition of the nitrogenous portion, 
for it is quite generally recognized that the substitution of 
oleomargarine is not injurious to health. It is a not infre- 
quent practice, however, as remarked in the previous chap- 
ter, to incorporate a large amount (sometimes as high as 
33 per cent.) of curd and other nitrogenous matters in fresh 
butter. If this is kept for any length of time, a decomposi- 
tion is liable to occur which may have serious effects. Other 
determinations that are usually made are the water and salt. 

The term " oleomargarine " is usually applied to a mixture 
of refined lard, " oleo oil," which is mainly the olein of beef fat, 
and cottonseed oil. Ordinarily a small proportion of butter 
is added and the product is generally churned with milk. 

A comparatively recent form of butter substitute which 
finds extensive use in some sections of the country is 
"process," or "renovated," butter. The raw material, or 
" stock," used for the manufacture of this consists of butter 
which cannot be sold as butter either because of deteriora- 
tion through rancidity or moulding or because, through care- 
lessness on the part of the makers, it possesses an unattractive 
appearance or flavor. The chief recruiting-ground for this 
material is the country grocery store. The fat, separated 
from the curd by melting and settling, is aerated to remove 
disagreeable odors and leave it nearly neutral. This is then 
emulsified with fresh milk which has been inoculated with 
a bacterial culture, and the whole is chilled, granulated, 
and churned. The butter is then worked and packed for 
market in the usual manner. The character of the prod- 



food: analytical methods: butter. 193 

uct has much improved since the early days of the 
industry, the best grades now approximating- the lower 
grades of creamery butter. 

The " aroma " of butter seems to be connected with the 
decomposition produced by the action of bacteria on the 
casein and the small amount of milk-sugar that is present, 
and not with any change in the fats; there is no evidence, 
however, that any unwholesome effect is produced by the 
aroma-giving organisms. 

The rancidity of butter-fat is generally considered to be 
due to decomposition and oxidation of the fatty acids, espe- 
cially the unsaturated ones, the amount of change depending" 
on conditions of light, heat, and exposure to air. 

Examination of the Fat. — The fat is first separated 
from the other constituents of the butter so that it may be 
weighed out for the various tests. 

Directions. — Melt a piece of butter, about two cubic 
inches, in a small beaker placed on top of the water-bath so 
that the temperature shall not rise above 50°-6o°. After 
about fifteen minutes the water, salt, and curd will have set- 
tled to the bottom. (A better separation may be secured 
by dividing the melted sample equally between two test-tubes 
and whirling them for 3-4 minutes in a centrifugal machine.) 
Place a bit of absorbent cotton in a funnel, previously waimed, 
and decant off the clear fat through the cotton into a second 
beaker, taking care that none of the water or curd is brought 
upon the filter. When the filtered fat has cooled to about 40 
place a small pipette in the beaker and weigh the whole. 

By means of the pipette the desired amount of fat is taken 
out, the pipette replaced in the beaker, and the whole again 
weighed. The difference in weight gives the exact amount 
of fat taken. It is a saving of time, however, if several por- 
tions are to be weighed out, to make the weights one after 



194 AIR, WATER, AND FOOD. 

another, so that one weight will suffice for a determination. 
Weigh out thus : Two portions of 5 grams each into 250-c.c. 
round-bottomed flasks for the Reichert-Meissl method, one 
portion of 2,5 to 3 grams into a 500-c.c. beaker for Hehner's 
process, two portions of about .35 to .5 gram each into 300-c.c. 
.glass-stoppered bottles for determination of the iodine value. 
In the case of the larger portions, weigh only to the nearest 
milligram. 

(1) Reichert-Meissl Number for Volatile Fatty Acids. 
— Directions. — To the fat in the 250-c.c. flasks add 2 c.c. of 
strong caustic potash (1:1) and 10 c.c. of 95 per cent, 
alcohol. Connect the flask with a return-flow condenser 
and heat on a water-bath so that the alcohol boils vigorously 
for 25 minutes. At the end of this time disconnect the flask 
and evaporate off the alcohol on a boiling-water bath. After 
the complete removal of the alcohol add 140 c.c. of re- 
cently boiled distilled water which has been cooled to about 
50 . The water should be added slowly, a few cubic centi- 
meters at a time. Warm the flask on the water-bath until 
a clear solution of the soap is obtained. Cool the solution to 
about 6o° and add 8 c.c. of sulphuric acid (1:4) to set free 
the fatty acids. Drop two bits of pumice, about the size of 
a pea, into the flask, close it by a well-fitting cork, which is 
tied in with twine, and immerse it in boiling water until the 
fatty acids have melted to an oily layer floating on the top 
of the liquid. Cool the flask to about 6o°, remove the cork, 
and immediately attach the flask to the condenser. 

Distil no c.c. into a graduated flask in as nearly thirty 

minutes as possible. Thoroughly mix the distillate, pour the 

whole of it through a dry filter, and titrate 100 c.c. of the 

N . 

mixed filtrate with — ■ sodium hydroxide, using phenol- 

phthalein as an indicator. Multiply the number of cubic centi- 



food: analytical methods: butter. 195 

meters of alkali used by eleven-tenths, and correct the reading 

also for any weight of fat greater or less than 5 grams. 

For example, if 5.3 grams of butter-fat are used, and 100 

N 
c.c. of the distillate require 27.4 ex. of — NaOH, no c.c. 

would require 2.7.4X^=30.14 c.c. Then 5.3 : 30.14 = 
5 : x . #=28.4. x is the Reichert-Meissl number. 

Notes. — The Reichert-Meissl number for genuine butter 
varies from 24 to 34; the average usually taken is 28.8. 

Cocoanut oil gives a value of 6-8; other edible fats and oils 
have a value usually less than 1 . 

The presence of cocoanut oil is readily shown by the Reichert- 
Meissl number taken in connection with the saponification 
value, that is, the number of milligrams of potassium hydroxide 
required to saponify one gram of the fat. (For a description 
of the method of determining this see Lewkowitsch: Oils, Fat, 
and Waxes, or Gill: A Short Handbook of Oil Analysis). The 
Reichert-Meissl number is higher in butter fat than in cocoanut 
oil, while the saponification value is lower. In pure butter 
fat the value of the expression (Saponification value — Reichert- 
Meissl number — 200) varies from 3.4 to 4.1; in pure cocoanut 
oil it runs from 47 to 50.7.* 

When the fat is treated with potash it is decomposed, the 
glycerine being set free, and the potassium salts of the fatty 
acids, that is to say, the potassium soaps are formed. Hence 
the process is called saponification. For butyric acid the 
reaction may be expressed 

C 3 H 5 (C 3 H T COO) 3 + 3KOH = 3 C 3 H 7 COOK + C 3 H 5 (OH) 3 . 

The alcohol is used to dissolve the fat. But at the 
moment the butyric acid is set free it tends to combine with 
the alcohoi to form a volatile ether: 

C 3 H 7 COOH + C 2 H 5 OH = QHCOOC 2 H 5 + H 2 0. 



Juckenack and Pasternack: Ztschr. Nahr. Genussm., 7 (1904), 193. 



I96 AIR, WATER, AND FOOD. 

The object of the return-flow condenser is to prevent the 
escape of this volatile ether and to allow of its complete 
saponification. 

If the water used to dissolve the soap is added too rap- 
idly, the soap may be decomposed with the liberation o c the 
fatty acids: C 3 H 7 COOK + H 2 = C 3 H 7 COOH + KOH. 

The fatty acids are set free at the proper time by means 
of sulphuric acid, and the volatile acids distilled off and 
ntrated. The pumice is added to prevent explosive boiling. 

The whole of the volatile acids do not pass over into the 
distillate, but only a part, the amount depending upon the 
rate of distillation and the volume of the distillate Hence, m 
order to get uniform results, it is necessary to follow the pre- 
scribed procedure with great care. 

(2) Hehner's Method for Direct Determination of 
the Fixed Fsttv Acids. — Directions. — To the portion of 
2.5 grams weighed out into the 500-c.c. beaker add 1 c.e. of 
caustic potash and 20 c.c. of 95 per cent, alcohol. Cover 
the beaker with a watch-glass and heat it on the water-bath 
until the liquid is clear and homogeneous. As it is not essen- 
tial to prevent the escape of the volatile acids, the use of a 
return-flow condenser is not necessary. Evaporate off the 
alcohol on the water-bath and dissolve the soap in about 
400 c.c. of warm distilled water. When the soap is com- 
pletely dissolved add 10 c.c. of hydrochloric acid (sp. gr. 
1.1 2), and heat the beaker in the water-bath almost to boil- 
ing until the clear oil floats. Meanwhile dry and weigh a 
thick filter in a small covered beaker. Allow the solution 
to cool until the fat forms a solid cake on top ; filter the clear 
liquid and finally bring the solid fats upon the weighed 
filter. Wash the beaker and fat thoroughly with cold water, 
then wash out the fat adhering to the beaker with boiling 
water, which is poured through the filter, taking care that 



food: analytical methods: butter. 197 

the filter is never more than two-thirds full. If the filter paper 
is of good texture and thoroughly wet beforehand it will retain 
the fatty acids completely. If, however, oily particles are 
noticed in the filtrate, cool it by adding pieces of ice, remove 
the solidified particles with a glass rod and transfer them to 
the filter. Cool the funnel by plunging it into cold water, 
remove the filter, place it in the weighing-beaker and dry it at 
ioo° to constant weight. The fat should be heated about an 
hour at first, then for periods of about thirty minutes, until the 
weight is constant within 2 mgs. 

Notes. — 87.5 per cent, is usually taken as the proportion 
of fixed fatty acids in butter-fat ; 88 and 89 per cent, have 
been frequently found. All other fats yield from 95 to 96 
per cent, of insoluble fatty acids. 

(3) Determination of Iodine Value. — This method is 
based on the fact that certain of the fatty acids, notably 
the "unsaturated acids," as oleic acid, C 17 H 33 COOH, take 
up the halogens with the formation of addition products. 

Directions. — Dissolve the fat in the 300-c.c. bottles in 

10 c.c. of chloroform. Add 30 c.c. of the iodine solution 

from a pipette or glass-stoppered burette, and allow the 

bottles to stand with occasional shaking for fifteen minutes. 

Add 10 c.c. of 20 per cent, potassium iodide solution, then 

100 c.c. of distilled water, and titrate the excess of iodine 

N 
with — sodium thiosulphate until the solution is faintly 

yellow. Add 2-3 c.c. of starch solution and titrate to 
the disappearance of the blue color. Calculate the result 
in grams of iodine absorbed by 100 grams of fat. This is 
called the Iodine Number, or Iodine Value. 

At the time of making the determination carry out two 
* ' blanks ' ' in exactly the same way except that no fat is used 
and only 20 c.c. of the iodine solution is added. 

Standardization of the Thiosulphate Solution. — As this is 



198 AIR, WATER, AND FOOD. 

not permanent, its strength should be determined by means 
of the standard potassium bichromate solution, 1 c.c. of 
which is equivalent to 0.0 1 gram of iodine. 

Measure 20 c.c. of the potassium bichromate from a 
pipette into an Erlenmeyer flask. Add 5 c.c. of potassium 
iodide, 100 c.c. of water, and 5 c.c. of strong hydrochloric 
acid. Titrate the liberated iodine with the thiosulphate solution 
until the color has almost disappeared, then add starch solution 
and continue the titration until the blue color changes to a 
sea-green, due to the formation of chromium chloride. The 
iodine is liberated in accordance with the following equation: 

K 2 Cr 2 7 + 14HCI + 6KI = 8KC1 + 2 CrCl 3 + 7 H 2 + 61. 

Calculation of Results. — Example. — From the standardi- 
zation, 

16.07 c.c. thiosulphate = 20 c.c. bichromate =0.200 gram I; 
1 c.c. thiosulphate =0.0125 gram I. 
Also, from blank, 

20 c.c. iodine solution =42.40 c.c. thiosulphate; 
1 c.c. iodine solution = 2.12 c.c. thiosulphate. 
If 30 c.c. iodine solution have been added to 0.6542 
grams of fat, then 30X2.12=63.60 c.c. is the equivalent 
amount of thiosulphate solution; and if 44.85 c.c. thio- 
sulphate were used to titrate excess of free iodine, 63.60 — 
44.85 = 18.75 c.c. is the amount of thiosulphate equivalent 
to the iodine combined with the fat. Then, since 1 c.c. 
thiosulphate is equivalent to 0.0125 gram free iodine, 

— —^-7 — '■ X 100 =35.83 grams of iodine combined with 

0.0542 

100 grams fat. 

Notes. — It is assumed that 100 grams of pure butter-fat 

absorb 30-40 grams iodine; oleomargarine, 63-75 grams; 

olive-oil, 83 grams; and cottonseed-oil, 106 grams. 



food: analytical methods: butter. 199 

The products formed by the action of iodine on the fats 
are mainly addition products with a slight proportion of 
substituted bodies. Thus the unsaturated olein, 

(C 17 H 33 COO) 3 C 3 H 5 , 

takes up six atoms of iodine, forming an addition product^ 
di-iodo-stearin, (C 17 H 33 I 2 COO) 3 C 3 H 5 . 

The method in general use for determining the iodine 
value of fats and oils has been that of Baron Hubl,* an 
alcoholic solution of iodine and mercuric chloride being 
used as the reagent. The method here described, due to 
Hanust, has the advantage that the solutions keep better, 
remaining practically unchanged for several months, and 
that the action is about sixteen times as rapid. For the 
fats and for oils with low iodine values the results are very 
close to the figures obtained by the Hubl process. If it is 
desired to carry out the determination by the older method, 
directions can be found in any standard work on the analysis 
of oils. 

Great care should be taken that there is no change in 
temperature between the time of measuring the solution of 
iodine for the blanks and for the determinations, since the 
high coefficient of expansion of acetic acid may cause a material 
error. 

The Spoon Test or " Foam " Test. — Melt a piece of the 
sample as large as a small chestnut in an ordinary tablespoon 
or a small tin dish. A test-tube can be used if desired. Use 
a small flame and stir the melting fat with a splinter of wood 
(such as a match). Then increase the heat so that the fat 

* Ding. Poly. J., 253, 281; /. Soc. Chem. Ind., 3 {1884), 641. 
•j" Ztschr. Unters. Nahr. u. Genussm., 4 (ipoi), 913. 



200 AIR, WATER, AND FOOD. 

shall boil briskly, and stir thoroughly, not neglecting the outer 
edges, several times during the boiling. 

Oleomargarine and renovated butter boil noisily, usually 
sputtering like a mixture of grease and water when boiled, 
and produce little or no foam. Genuine butter usually boils 
with much less noise and produces an abundance of foam. 
The difference in regard to the foam is very marked. 

Note also the appearance of the particles of curd after the 
boiling. With genuine butter these will be very small and finely 
divided, hardly noticeable in fact, while with oleomargarine 
and renovated butter the curd gathers in much larger masses 
or lumps. 

Notes. — This simple method is of value for giving a quick 
decision regarding a sample, and is especially useful for the 
detection of renovated butter. The differences in the composi- 
tion of butter-fat brought about by renovation are so slight 
that chemical methods are here of no avail. 

The spoon test, however, will distinguish in the great 
majority of cases between genuine butter on the one hand and 
oleomargarine and renovated butter on the other; the index 
of refraction or the chemical methods just described readily 
distinguish between the two latter. 

Physical Methods. — Microscopic Examination. — Pure, fresh 
butter is not ordinarily crystalline in structure. Butter which 
has been melted, however, and fats which have been liquefied 
and allowed to cool slowly show a distinct crystalline structure, 
especially by polarized light. If only fresh butter were sold, 
and all adulterants had been previously melted and slowly 
cooled, this method would be all that would be necessary for 
the detection of adulteration. As it is, however, it is most 
useful in making comparative examinations of samples which 
have been subjected to the same conditions. From an examina- 
tion of the accompanying plate,* which shows the appearance 

* From photomicrographs by A. G. Woodman and A. I. Kendall, 1900. 



food: analytical methods: butter. 201 

by polarized light of four samples of known origin which were 
melted and cooled slowly under exactly similar conditions, it 
will be seen that, while the differences are noticeable, they are 
not sufficient in all cases to form a basis for absolute identi- 
fication. 

About the most that can be said is that if a small bit, about 
the size of a pin-head, of the fresh, unmelted sample, is taken 
from the center of the mass and pressed out on a slide by gentle 
pressure on the cover glass, it ought to show a fairly uniform 
field if examined with a one-sixth objective, using polarized 
light and a selenite plate. Other fats melted and cooled, and 
mixed with butter, generally show a crystalline structure and 
a variegated color with the selenite plate. 

For a further discussion of this point the student is referred 
to Bulletin 13, U. S. Dept. Agric, Part I, pp. 29-40; Part 
IV, pp. 449-455- 

Specific Gravity. — This is most conveniently determined 
at ioo° C. by means of the Westphal balance (see Allen, The 
Analyst, n, 223; also Bull. 13, Part IV, pp. 430-431). The 
pyknometer method is, however, the one adopted by the Asso- 
ciation of Official Agricultural Chemists as the official method. 
See Bulletin 107, p. 130. 

Melting Point. — This may be determined by the capillary- 
tube method as generally employed for organic substances and 
described in text books on organic analysis. (See for instance, 
Mulliken: Identification of Pure Organic Compounds, Vol. I, 
p. 218.) Wiley's method, however, which is the official method 
of the A. O. A. C, has the advantage that it avoids the incorrect 
results which are sometimes obtained with other methods due 
to the adherence of the melting fat to solid surfaces. A descrip- 
tion of the method will be found in Bull. 107, p. 133. 

Refractive Ina]ex. — The determination of the refractive index 
is especially valuable in food analysis on account of the ease 



202 



AIR, WATER, AND FOOD 



and rapidity with which the determination can be made and 
the fact that so little of the substance is necessary for the 
determination. Various forms of refractometers are used for 
the purpose, a fairly complete description of which will be found 




1 [l 'H fl 



Fig. 14. 



in some of the larger works, such as Leach: Food Inspection 
and Analysis, or Vaubel:' Quantitative Bestimmung organischer 
Verbindungen. The instrument having the widest range is 
the Abbe refractometer, in which the index of refraction is 
determined by measuring the total reflection produced by a 
very thin layer of the melted fat, placed between two prisms 



food: analytical methods: butter. 203 

of flint glass. This instrument, fitted with water- jacketed 
prisms is shown in Fig. 14. 

Directions. — Revolve the whole instrument on the axis b until 
it reaches the stop provided, then open the prism casing AB by 
giving the pin v a half-turn (to the right). Be sure the prism 
surfaces are clean. It not, clean them carefully with a soft 
cloth and a little alcohol. Place a few drops of the melted 
sample directly on the surface of the prism and clamp the two 
together again by turning the pin v in the opposite direction. 
Now turn the instrument back (toward the observer) as far as 
possible and bring the " critical line " into the field of vision 
of the telescope. This is done by holding the sector 5 firmly 
with the hand and revolving the double prism by means of the 
alidade / until the field is divided into a light and a dark 
portion. If the line is not sharp focus the ocular 01 the tele- 
scope. If it is colored it is due to dispersion of trie light by 
the liquid and should be corrected by revolving tne compen- 
sator T by the milled screw M. The correction is made by a 
system of two revolving Amici prisms in the lower part of the 
telescope. Adjust the critical line so that it falls on the inter- 
section of the cross hairs of the telescope. Observe the temper- 
ature by the thermometer inserted in the prism casing. In the 
case of solid fats a sufficiently high temperature should be 
maintained by a current of warm water to keep the sample 
well above its melting point. A temperature of 30-40 C. is 
usually sufficient. Do not let the temperature rise above 70 
or the prisms may be injured. Read the index of refraction 
directly through the small lens L, estimating the fourth decimal. 
Calculate the value for the refractive index at 25 ° C. 

Notes. — The index of refraction decreases with rising tem- 
perature. With the common oils and lats the change for each 
degree is very nearly a constant, amounting to 0.000365. 
Leach and Lythgoe* have devised a sliding scale by means of 

* J. Am. Chem. Soc. (1904), 1193. 



204 AIR, WATER, AND FOOD. 

which the temperature correction may be readily made without 
reference to tables. 

The values of wff for genuine butter lie between 14590 
and 1.4620; for oleomargarine the values range from 1.4650 to 
1.4700. 

The correctness of the adjustment of the instrument may 
be tested by the " test-plate " which comes with it, using 
monobromnaphthalene, or by means of distilled water. The 
theoretical value for the refractive index of water at 18 C. is 

1.3330. 

Determination of Water. — Directions. — Weigh 2 grams 
of butter into a shallow metal dish having a flat bottom two 
inches in diameter and containing a slender stirring-rod two 
and a half inches long. Heat the butter in the oven at ioo° 
C. for thirty minutes, cool in a desiccator, and weigh. Heat 
again for periods of fifteen minutes, until the weight remains 
constant within 2 or 3 milligrams. During the process of heat- 
ing stir the butter frequently to hasten evaporation of the water. 

Determination of Salt.- -Directions. — Weigh 10 grams 

of butter in a small beaker, add 30 c.c. of hot water, and 

when the fat is completely melted transfer the whole to a 

separately funnel. Shake the mixture thoroughly, allow 

the fat to rise to the top, and draw off the water, taking care 

that none of the fat-globules pass the stopcock. Repeat the 

operation four times, using 30 c.c. of water each time. Make 

the washings up to 250 c.c, mix thoroughly, and titrate 25 

N 
c.c. in a six-inch porcelain dish, using — silver nitrate with 

potassium chromate as an indicator. 

Complete Analysis of Butter in One Sample. — Direc- 
tions. — Weigh about 2 grams of butter into a platinum 
Gooch crucible, half-filled with ignited fibrous asbestos, and 
dry it at ioo° C. to constant weight. The loss in weight is 
the amount of water. Then treat the crucible repeatedly 




A. Butter X 30. 

C. Oleomargarine X 30. 



B. Beef-fat X 30, 
D. Lard X 30. 



food: analytical methods: butter. 205 

with small portions of petroleum ether, using- gentle suction, 
and again dry it to constant weight. The difference between 
this and the preceding weight will be the amount of fat. 
Now carefully heat the crucible over a sma 1 l flame or in a 
muffle until a light grayish ash is obtained. The loss in 
weight is the amount of curd, and the residual increase in 
weight over that of the crucible and asbestos is the ash. If de- 
sired, the salt may be washed out of the ash and determined 
by titration with silver nitrate after neutralizing the solution 
with calcium carbonate. 

FLOUR, PREPARED CEREALS, ETC. 

This class of foodstuffs is usually in a dry form and not 
liable to rapid change by micro-organisms, and the examina- 
tion consists in the determination of their " food value." This 
may require a simple analytical process, as in the case of the 
quantity of nitrogen in a sample of " gluten " sold for diabetic 
patients, or in the case of a brand of flour to be used in a 
hospital or State institution. It may also require an estimation 
of the available food-material, as in the case of two kinds of 
beans or corn. The results of chemical analysis will often put 
the statements made on packages of breakfast cereals in a 
different light. 

Owing to the extensive use at present of various cereal 
breakfast foods, many of which are modified from their original 
composition by cooking or treatment with malt, the extent to 
which the starch has by this treatment been converted to 
soluble forms is also an important question for consideration. 
The actual determination of digestibility belongs to physio- 
logical chemistry and need not be taken into consideration here. 

Moisture. — Directions. — Spread about 2 grams of the finely 
ground material in a thin layer on a watch-glass and dry it 
in the oven at ioo° C. for five hours. On account of the ready 



206 AIR, WATER, AND FOOD. 

absorption of moisture by the dried sample, the use of clipped. 
watch-glasses will be found advantageous. 

Note. — With some substances drying in a current of hydrogen 
or some inert gas may be necessary, but for most cereals the 
method given will be found satisfactory. 

Ash. — Directions. — Weigh about 2 grams into a platinum 
dish, such as is used for the determination of solids in milk, 
and char it carefully. Ignite at a very low red heat until the 
ash is white, preferably in a muffle. 

Notes. — If a white ash cannot be obtained in this manner, 
exhaust the charred mass with water, collect the insoluble 
residue on a filter, burn it, add this ash to the residue from 
the evaporation of the aqueous extract and heat the whole at 
a low red heat until the ash is white. 

Some cereals, such as whole wheat and bailey, will act 
destructively on platinum dishes, on account of the phosphates 
present but can be ignited safely in platinum in the muffle. 

Ether Extracts: Fats and Oils. — Directions. — Place the 
residue from the determination of moisture, as described above, 
in an extraction-cone and extract it with pure anhydrous 
ether for sixteen hours. Evaporate off the ether and dry the 
residual fat at the temperature of boiling water to constant 
weight. 

The ether extract of cereals is not pure fat but may contain 
more or less coloring matter or resins. Petroleum ether can be 
used for the extraction, giving results not essentially different 
from those obtained with anhydrous ethyl ether. 

Total Proteids: Determination of Nitrogen by the 
Kjeldahl Process. *— --Principle. — Oxidation of carbon and 
hydrogen, and conversion of organic nitrogen to ammonium 
sulphate by means of boiling sulphuric acid in presence of 

* Ztschr. anal. Chem., 22 {1883), 366. 



food: analytical methods: butter. 207 

mercury, the latter acting as a carrier of oxygen, and being 
converted to mercuric sulphate. Precipitation of mercury by 
potassium sulphide to prevent the formation of mercur-ammo- 
nium compounds when the solution is made alkaline. Setting 
free of ammonia by neutralization of the acid by potassium 

hydroxide. Distillation of ammonia into a measured quantity 

N 
of — acid. Titration of excess of acid. 
10 

Directions. — Transfer about 0.5 gram of the finely divided 
substance from a weighing-tube to a pear-shaped digestion 
flask, add 10 c.c. of concentrated sulphuric acid free from 
nitrogen, and 0.2 gram (three small drops) of metallic mercury. 
Place a small funnel in the neck of the flask, which should be 
supported in an inclined position on wire gauze and heated 
with a small flame until frothing has ceased and the liquid boils 
quietly. Then increase the heat and boil the solution for at 
least half an hour after it becomes colorless. Allow the flask 
to cool for a minute or two, and add a few crystals of potassium 
permanganate until the liquid has acquired a slight green or 

purple color. 

N 
Measure 25 c.c. of — acid from a burette into a 300-c.c. 

Erlenmeyer flask and place the condenser-tip beneath the 
surface of the liquid, adding a little water, if necessary, to 
seal it. 

Transfer the digestate with several small portions of distilled 
water to the distilling flask of the apparatus, add 20 c.c. of 
potassium sulphide solution, and connect the flask with the 
condenser. Add 50 c.c. of caustic potash through the separa- 
tory funnel, and distil off the ammonia by steam. When 200 
c.c. have distilled over, remove the collecting-flask, after rinsing 
off the condenser-tip with distilled water, and titrate the excess 

N 
of acid with — sodium hydroxide, using methyl orange or 



2o8 

cochineal as indicator. If using new reagents, a blank deter- 
mination should be made with 0.5 gram of cane-sugar in order 
to reduce any nitrates present which might otherwise escape 
detection. 

Notes. — The temperature during the digestion must be 
maintained at or near the boiling-point of the acid, since at a 
lower temperature the formation of ammonia is incomplete. 

The process is considered by Dafert * to take place in four 
steps: (1) the sulphuric acid takes the elements of water from 
the organic matter; (2) the sulphur dioxide produced by the 
action of the residual carbon on the sulphuric acid exercises 
a reducing action on the nitrogenous bodies; (3) the nitro- 
genous substances formed in this way are converted to am- 
monia by a process of oxidation; (4) the ammonia formed is 
fixed by the acid as ammonium sulphate. 

In some cases the potassium permanganate is necessary 
to insure the complete conversion of the nitrogenous bodies 
into ammonia, although it is probable that its use is unneces- 
sary in the majority of analyses. 

The Kjeldahl process in the form outlined above is not 
applicable to the determination of nitrogen in the form of 
nitrates. In order to render it of more general application 
various modifications of the method have been proposed, the 
one generally used in this country being that suggested by 
Scovell.t In this method salicylic acid is used with the sul- 
phuric acid, being converted by the nitrate into nitro-phenol. 
By the use of sodium thiosu'phate or zinc-dust this is reduced 
to amido-phenol. The amido-phenol is transformed into am- 
monium sulphate by the heating with sulphuric acid, the use 
of mercury being absolutely necessary in this case to secure 



* Ztschr. anal. Chem., 24 (1885), 455- 
t U. S. Dept. Agr., Bull. 16 (1887), 51 



food: analytical methods: cereals. 209 

the complete transformation. It is true also that certain other 
nitrogenous bodies, notably the alkaloids and certain organic 
bases, do not yield all their nitrogen to the Kjeldahl process 
without modifications which complicate the method. For a 
discussion of the efficiency of these various modifications the 
student is referred to a paper by Sherman and Falk.* 

The per cent, of proteids may be found by multiplying the 
per cent, of nitrogen by an appropriate factor, the one in general 
use being 6.25. Recent work has shown, however, that most 
of the proteids of cereals contain more than 16 per cent, of 
nitrogen, so that the factor 6.25 gives results that are too high. 
Because all the older work was calculated on this factor, it is 
still generally used, nevertheless. 

Kjeldahl-Gunning Method. — The Gunning method can be 
used in all cases where the Kjeldahl-Wilfarth modification, just 
described, is employed, and in some ways it is simpler. 

The digestion and distillation are carried out as described 
on page 207, using the same amount of sample, together with 
20 c.c. of concentrated sulphuric acid and 10 grams of powdered 
potassium sulphate. No mercury and consequently no potas- 
sium sulphide is used. 100 c.c. of the potash should be added 
instead of 50. 

Note. — The potassium sulphate is added to raise the boiling 
point of the sulphuric acid and thus shorten the time required 
for the digestion. 

Carbohydrates. — The total carbohydrates, often stated in 
analyses as " nitrogen-free extract," may be readily obtained 
by subtracting from 100 the sum of the percentages 
of the other constituents, viz., moisture, ash, ether extract, 
and nitrogenous bodies. In many cases, however, espe- 
cially with the cooked or treated cereals and with such 

* J. Am. Chem. Soc. {1904), 26, 1469. 



2IO AIR, WATER, AND FOOD. 

classes of cereal preparations as infant or invalid foods, a 
further study of the carbohydrates is desirable. These are 
made up of two general classes: (a) soluble carbohydrates, 
including sugars, as sucrose, dextrose and maltose, dextrin 
and soluble starch, by the latter term being meant starch 
which is soluble in water but still gives the characteristic 
blue color with iodine, in distinction from some of the more 
completely broken-down forms like dextrin, which no 
longer give blue or purple colors with iodine; (b) insoluble 
carbohydrates, including starch, pentosans, lignin bodies, and 
cellulose. The three latter occur chiefly in the husk or 
envelope of the grain or in the woody fibre of the plant. 
The pentosans or gums are distinguished from one another 
by the formation of specific sugars upon hydrolysis with 
acids. For ordinary analytical purposes it is sufficient to 
determine the lignin and cellulose together as " crude fibre." 
Since the exact procedure to be followed in the determina- 
tion of the carbohydrates varies largely with each specific 
case, only a general outline can be presented here. 

Sugars. — The finely ground material, previously dried 
and extracted with ether for the removal of crude fat, is 
extracted with 85 per cent, alcohol. In the extract the 
reducing sugars may be determined by means of Fehling's 
solution as described on page 181, and the sucrose deter- 
mined in the same way after inversion with hydrochloric 
acid. 

Dextrin and Soluble Starch. — The residue from the ex- 
traction of the sugars is treated for eighteen to twenty-four 
hours with water at laboratory temperature with frequent 
agitation, made up to definite volume, and filtered. This 
may be tested with iodine, and if no blue color is produced, 
evaporated to small volume, and the dextrin converted to 
dextrose by dilute hydrochloric acid and determined by 



food: analytical methods: cereals. 211 

Fehling's solution. In some few cases, however, a blue 
color with iodine may indicate the presence of soluble starch, 
in which case an aliquot part of the filtrate may be treated 
with an excess of barium hydroxide to precipitate the starch. 
In the filtrate from this precipitate the dextrin is deter- 
mined by inversion and copper reduction as before. The 
difference between the dextrin thus found and the first 
determination gives the soluble starch. 

Starch. — The methods for the determination of starch 
vary with the condition in which the starch is found. In the 
case of nearly pure starch it may be converted into dextrose 
by boiling with dilute acid, the dextrose being then deter- 
mined by Fehling's solution in the usual way. Hot acids, 
however, cannot be used to convert starch in the natural 
state, as it is found in cereals, because other carbohydrate 
bodies, especially the pentosans, become soluble under these 
conditions and the results are too high. In such cases the 
starch is brought into solution by treatment with diastase or 
by heating with water under pressure. The results obtained 
by direct acid hydrolysis, however, in cases where the highest 
accuracy is not required, may be sufficient and the method is 
much quicker and easier of execution than the digestion with 
diastase. 

Direct Acid Hydrolysis. — Directions. — Weigh out from 2 
to 5 grams of the sample, depending upon the amount of starch 
present, and wash on a filter with five successive portions of 
10 c.c. each of ether. Allow the ether to evaporate from the 
residue and then wash it with 10 per cent, alcohol until free 
from soluble carbohydrates. 150 c.c. of the dilute alcohol is 
generally sufficient, but if much reducing sugar or dextrin is 
present, as may be the case with malted cereals, more will be 
necessary. Wash the residue from the filter with 200 c.c. of 
water into a 500 c.c. graduated flask, add 20 c.c. of hydrochloric 
acid, sp. gr. 1.125, place a funnel in the neck of the flask to 



212 AIR, WATER, AND FOOD. 

retard evaporation, and heat in a boiling water bath for two and 
one-half hours. Cool, nearly neutralize with sodium hydroxide 
and make up to 500 c.c. Filter, and determine dextrose in an 
aliquot portion, 25 or 50 c.c., of the filtrate, using the method 
described on page 181. Convert dextrose to starch by the 
factor 0.9. 

Note. — The washing to remove soluble carbohydrates is 
performed with dilute alcohol rather than with water because 
the former is less likely to carry starch granules through the 
paper. The sugar solution when added to the Fehling's solution 
should be clear and only faintly acid. It should in general 
contain not more than 0.5 per cent, of reducing sugar. 

Determination with Diastase. — Directions. — Treat 2 to 5 
grams of the sample with ether and dilute alcohol, as in the 
previous method, and wash the residue into a 250-c.c. flask 
with 50 c.c. of water. Heat slowly to boiling, or immerse the 
flask in boiling water, until the starch gelatinizes, stirring 
constantly to prevent the formation of lumps. Cool to 55 ° C, 
add 20-40 c.c. of malt extract, and keep the solution within 
two degrees of the stated temperature for an hour or until the 
solution no longer gives the starch reaction with iodine under 
the microscope. In either case heat the solution again to 
boiling to gelatinize any remaining starch granules, test again 
and if starch is found, cool to 55 C, and treat as before, using 
a fresh portion of malt extract. Continue this treatment until, 
when carefully examined under the microscope, a drop of the 
solution fails to give the iodine reaction for starch. Cool, 
make up to 250 c.c. and filter through a dry filter. Transfer 
200 c.c. of the filtrate to a 500-c.c. graduated flask, add 20 c.c. 
of hydrochloric acid, sp. gr. 1.125, and carry out the determina- 
tion as described in the preceding method. 

A blank determination must be carried through, using 50 
c.c. of water and exactly the same amount of malt extract as 



food: analytical methods: cereals. 213 

vised in the regular procedure, in order to correct for the cupric 
reducing power of the malt extract. 

Malt Extract. — Treat 40 grams of fresh coarsely ground malt 
several hours with 200 c.c. of water, shaking occasionally. 
Filter and add a few drops of chloroform to prevent the growth 
of molds. 

Notes. — The action of the diastase on the gelatinized starch 
is to convert it into maltose and dextrin, that is, into soluble 
bodies that can be separated by filtration from the pentosans 
and other carbohydrates that give the high results in the direct 
acid method. By the action of acid (hydrolysis) the maltose 
and dextrin are converted to dextrose. 

The determination should, if possible, be carried through 
without interruption. In case this cannot be done salicylic 
acid may be used to prevent fermentation, not adding it, how- 
ever, until after the digestion with diastase. 

If the malt itself is not readily procurable, certain forms 
of prepared diastase are on the market and may be found more 
convenient either for analytical use or for purposes of illustra- 
tion. When possible, however, it is preferable to use the freshly 
prepared malt extract, as the prepared diastase, made at 
different times and from separate portions of malt, may show 
great differences in hydrolytic power. 

It is sometimes convenient to use freshly collected saliva, 
this being free from carbohydrate. In this case the digestion 
should be carried out at 38 C. instead of 55 C. 

Pentosans. — These are determined usually directly upon 
the original material. The methods in general use depend 
upon the conversion of the pentose substance into furfural 
by distillation with strong acid and the subsequent precipi- 
tation and estimation of the furfural. The latter may be done 
by treatment with phenylhydrazine acetate and formation of 
the furfural hydrazone, or by the formation of an insoluble 



214 AIR, WATER, AND FOOD. 

condensation product with phloroglucin according to the method 
of Councler. 

For the details of these methods reference may be made 
to Wiley, " Principles and Practice of Agricultural Analysis," 
Vol. Ill, p. 178 et seq., also an article by Sherman.* The 
phloroglucin method is given as a provisional method in BulL 
107 of the Bureau of Chemistry. 

Crude Fibre. — The Weende method, the method adopted 
by the Association of Official Agricultural Chemists, is based 
on the assumption that the starch and other digestible carbo- 
hydrates and proteid will be removed from the cereal by succes- 
sive digestion at a boiling temperature with acid and alkali of 
a definite strength. The complex body thus obtained is not a 
definite chemical compound, but may be considered as being 
composed largely of cellulose. 

Use 2 grams of .the finely ground sample and wash on a 
niter with 5 portions of 10 ex. each of ether. (The residue 
from the determination of " ether extract " can be used if 
desired.) 

Transfer the washed material to a 500-c.c. Erlenmeyer flask, 
add 200 c.c. of boiling 1.25 per cent, sulphuric acid, place a 
funnel in the neck of the flask and boil gently for 30 minutes. 
Filter on a ribbed filter and wash with several portions of boiling 
water. Transfer the precipitate by means of 200 c.c. of boiling 
1.25 per cent, sodium hydroxide in a small wash-bottle to the 
same 500-c.c. Erlenmeyer flask, and boil again gently for 30 
minutes. 

Filter on ignited asbestos in a Gooch crucible, wash with 
boiling water until free from alkali, then with 10 c.c. of alcohol, 
and finally with 10 c.c. of ether. Dry at the temperature of 
boiling water to constant weight. Ignite carefully at first, 

* /. Am. Chem. Soc, 19 {1897), 291. 



food: analytical methods: cereals. 215 

then at a low red heac until the organic matter is destroyed. 
Calculate the loss on ignition as " crude fibre." 

Note. — The filtration will be found to proceed fairly rapidly 
if the solution is filtered hot and care is taken to keep the 
residue from the filter as long as possible. 

The sulphuric acid and sodium hydroxide should be carefully 
prepared and the strength determined by titration. 

EXAMINATION OF FERMENTED LIQUORS. 
WINE. 

General Statements. — The object of a wine analysis is 
ordinarily to determine whether or not a wine is pure and 
unadulterated, or whether it has been properlv made. 
Special works furnish sufficient information concerning pro- 
cesses of manufacture, and it is essential to know here onlv 
the general composition of the grape-juice or "must" and 
how, by the natural process of fermentation, this may be 
altered in the finished product. 

The "must " contains sugars (mainly dextrose) ; dextrin; 
organic acids and salts, mainly tartaric and malic acids; 
salts of inorganic acids, chiefly phosphates, sulphates, and 
chlorides. Various extractive matters, which largely affect 
the color and flavor of the wine, together with a little tannin 
and albuminous substances, are also present. The wine will 
contain then, besides water, the following : Alcohol, glycerine, 
frequently some sugar that has escaped fermentation, ethers, 
which determine largely the "bouquet" of the wine, and 
more or less of the acids, salts, coloring and extractive mat- 
ters of the must, together with varying amounts of carbonic, 
acetic, and succinic acids. 

According to differences in their composition wines may 
be divided into various classes, such as " dry " w T ines, which 



2l6 AIR, WATER, AND FOOD. 

contain very little sugar, as distinguished from the sweet 
wines, in which a notable quantity of sugar has escaped 
fermentation, or to which an addition of sugar has been 
made subsequent to the main fermentation. Or they may 
be divided according to the content of alcohol into natural 
wines and those fortified by addition of alcohol, as port, 
sherry, and madeira. 

The composition of the wine may be changed, moreover, 
by the various methods which are used for its "improve- 
ment," such as fortification already mentioned, plastering, 
petiotization, etc. Information regarding these methods 
will be found in some of the larger works mentioned in the 
bibliography. 

The determinations of most value in judging the purity 
of wine are alcohol, glycerine, extract, ash, total and volatile 
acids. The actual percentages of these substances are not of 
so great value as certain relations between them, such as 
the ratio of ash to extract, extract to alcohol, alcohol to 
glycerine, alcohol to acids, and volatile to total acids. 
Examination for preservatives and foreign coloring matters 
should also be made. It should be remembered, however, 
in judging the quality of American wines that the standards 
of European practice are not entirely applicable and that 
further study will be necessary before even tentative stand- 
ards can be fixed. 

Specific Gravity. — This is to be taken by means of the 
Westphal balance or Sprengel tube at i5°.5 C. 

Notes. — Where the specific gravity of the sample is known, 
the various portions taken for analysis can be more conven- 
iently measured than weighed. The results can be calculated 
to per cent, by weight by dividing the results expressed as 
grams per ioo ex. by the specific gravity. 

Effervescing wines should, before analysis, be vigorously 



food: analytical methods: fermented liquors. 217 

shaken in a large flask to hasten the escape of carbon dioxide. 
The liquid may then be poured from under the foam into 
another vessel. 

Alcohol. — Principle. — The alcohol is obtained freed from 
everything but water, and its amount determined by ascertain- 
ing the specific gravity of the mixture, and taking the per cent, 
from the tables. 

Directions. — Measure (or weigh) 100 ex. of the wine into 
a 500-c.c. round-bottomed flask. Add 50 c.c. of water, neutralize 

N 
free acid with — sodium hydroxide, and add 0.5 gram of tannic 

acid, if necessary, to prevent foaming. Distil off about 95 to 
98 c.c. into a ioo-c.c. graduated flask. Fill up to the mark 
with distilled water, mix thoroughly, and take the specific 
gravity of the distillate at 15 °. 5 C. with a pyknometer. The 
percentage of absolute alcohol by volume corresponding to 
the observed density will be found in Table X, page 244. 

To find the alcohol by weight in the sample, multiply the 
per cent, of alcohol in the distillate as taken from the table, by 
the weight of the distillate and divide the result by the weight 
of the sample used. 

Notes. — The object of neutralizing the wine with sodium 
hydroxide is to prevent the distillation of volatile acids, prin- 
cipally acetic. A certain amount of volatile ethers may also 
pass over into the distillate, but in most cases it is so slight 
that its influence may be neglected. 

Normal wines ordinarily contain between 4.5 and 12 per 
cent, of alcohol except in the case of " fortified " wines, where 
the amount may be even 20 per cent. Fermentation does 
not yield more than about 14 per cent, of alcohol. 

Extract. — The method to be employed depends on the 
proportion of extract. A preliminary calculation should be 
made by the aid of the formula 

x = i+d— &'\ 



2.1 8 AIR, WATER, AND FOOD. 

where x is the specific gravity of the dealcoholized wine, d 
the specific gravity of the wine, and d' the specific gravity 
of the distillate obtained in the determination of alcohol. The 
value for x is found from Table XI, page 247. 

Dry Wines. — (Having an extract content of less than 
3 per cent.) Evaporate 50 c.c. on the water-bath to a 
sirupy consistency in a flat-bottomed platinum dish. Heat 
the residue in the oven at ioo° C. for two hours and a half, 
cool in a desiccator and weigh. 

Sweet Wines. — When the extract content is between 3 
and 6 per cent, treat 25 c.c. of the sample as described under 
dry wines. When the amount of extract exceeds 6 per cent, 
it is best to accept the result found from the table and not 
to determine it gravimetrically. 

Notes. — The gravimetric determination will be inac- 
curate with wines high in extract on account of the serious 
error caused by drying levulose at high temperatures. The 
figures in the table are based on determinations made at 
75 C. in vacuo. 

Wine made from the juice of ripe grapes rarely contains 
less than 1.5 per cent, of extract in the case of white wines 
and about 2.0 per cent, in the case of red wines. The 
amount of extract decreases of course with age. 

Alcohol-extract Ratio. — The municipal laboratory of 
Paris considers a wine "fortified" if the alcohol exceeds 4.5 
times the extract for red wines and 6. 5 for white wines. The 
amount of added alcohol is calculated by the municipal 
laboratory by subtracting the "natural" alcohol (extract 
X4.5 or 6.5) from the total alcohol. 

Ash. — Ignite the residue from the extract determination 
as described on page 206. 

Note. — The amount of ash in a natural wine averages 
about 10 per cent, of the extract, varying ordinarily be- 
tween 0.14 per cent, and 0.35 per cent. 



food: analytical methods: fermented liquors. 219 

Glycerine. — Evaporate 100 c.c. of wine in a porcelain 
dish on the water-bath to a volume of about 10 c.c, and 
treat the residue with about 5 grams of fine sand and with 
from 1.5 to 2 c.c. of milk of lime (containing 40 grams 
Ca(OH) 2 per 100 c.c.) for each gram of extract present, and 
evaporate almost to dryness. [With wines whose extract 
exceeds 5 grams per 100 c.c, heat the portion to be used in 
the determination of glycerine to boiling in a flask, and 
treat with successive small portions of milk of lime until 
it becomes, first, darker, and then light in color. When 
cool, add 200 c.c. of 96 per cent, alcohol (sp. gr. 0.81 18), 
allow the precipitate to subside, filter, and wash with 96 
per cent, alcohol (sp. gr. 0.81 18). Evaporate the filtrate 
to about 10 c.c, add about 5 grams of sand and from 1.5 
to 2 c.c of milk of lime, and proceed as before.] Treat 
the moist residue with 5 c.c of alcohol (96 per cent, by vol- 
ume), remove the substance adhering to the sides of the 
dish with a spatula, and rub the whole mass to a paste, with 
the addition of a little more alcohol. Heat the mixture on 
the water-bath, with constant stirring, to incipient boiling, 
and decant the liquid into a flask graduated at 100 and no 
c.c. Wash the residue repeatedly by decantation with 
10 c.c. portions of hot 96 per cent, alcohol. Cool the con- 
tents of the flask to 15 , dilute to the no-c.c mark with 
96 per cent, alcohol, and filter through a folded filter. 
Evaporate 100 c.c. of the filtrate to a sirupy consistency 
in a porcelain dish, on a hot, but not boiling, water-bath,, 
transfer the residue to a small glass-stoppered graduated 
cylinder with 20 c.c of absolute alcohol, and add three 
portions of 20 c.c each of absolute ether, with thorough 
shaking after each addition. Let stand until clear, then 
pour off through a filter, and wash the cylinder three times 
or more with a mixture of one part absolute alcohol to one 



220 AIR, WATER. AND FOOD. 

and one-half parts of absolute ether, pouring the wash- 
liquor also through the filter. Evaporate the filtrate to a 
sirupy consistency, dry for one hour at the temperature of 
boiling water, weigh, ignite, and weigh again. The loss in 
ignition increased by one-tenth gives the glycerine. 

Notes. — The ratio of glycerine to alcohol is of great 
importance in judging the purity of a wine. According to 
European standards in pure wines the glycerine-alcohol 
ratio varies from between 6 and 14 parts by weight of the 
former to 100 of the latter. The little work done on 
American wines indicates a lower ratio. 

Free Acids : Total Acidity Calculated as Tartaric 

N 
Acid. — Titrate 10 c.c. of the wine with — sodium hydroxide. 

The end-point is reached when a drop of the liquid placed 

upon faintly-red litmus paper produces a blue spot in the 

middle of the portion moistened. Calculate the results as 

N 
tartaric acid. One c.c. — sodium hydroxide =0.0075 gram 

of tartaric acid. 

Volatile Acids Calculated as Acetic Acid. — Measure 
50 c.c. of wine into a 3 00 -c.c. flask provided with a cork 
having two perforations. One is fitted with a tube 6 mm. in 
diameter and blown out to a bulb 40 mm. in diameter a short 
distance above the cork; this tube is connected with a con- 
denser. The other perforation carries a tube reaching nearly 
to the bottom of the flask and drawn out to a small aperture 
at its lower end; this is connected with a 500-c.c. flask con- 
taining water. Heat both flasks to boiling ; then lower the 
flame under that containing the wine, adjusting the flame so 
that the volume of liquid remains constant, and continue the 
distillation by means of steam until 200 c.c. have gone over. 



food: analytical methods: fermented liquors. 221 

N 
Titrate the distillate with — sodium hydroxide, using phe- 

nolphthalein as an indicator. Calculate the results as 

N 
acetic acid. One c.c. — sodium hydroxide =0.0060 eram 

10 

of acetic acid. 

Fixed Acids Calculated as Tartaric Acid. — These 
may be found by calculating the volatile acids as tartaric and 
subtracting the result from the total tartaric acid found by 
direct titration. 

Note. — The total acids in a wine vary usually between 
0.45 per cent, and 1.5 per cent. The acid content is fre- 
quently diminished by aging or by the separation of cream of 
tartar. The volatile acid should, in general, not be over 
0.12 to 0.16 per cent., depending upon the age of the wine. 
A wine properly made should not have the volatile acid, 
estimated as acetic, exceed one-fourth of the total free acid, 
calculated as tartaric. 

Coloring Matters: Detection of Coal-tar Dyes. — Double 
Dyeing Method of Sostegni and Carpentieri* — Fifty c.c. of the 
sample are diluted to 100 c.c. with water, filtered if necessary, 
acidified with from 2 to 4 c.c. of 10 per cent, solution of hydro- 
chloric acid, and a piece of woolen cloth which has been washed 
in a very dilute solution of boiling potassium hydroxide, and 
then washed in water, immersed in it and boiled for five to ten 
minutes. The cloth is removed, thoroughly washed in water, 
and boiled with very dilute hydrochloric acid solution. Then 
after washing out the acid the color is dissolved in a solution 
of ammonium hydroxide (1 to 50). With some of the dyes 
solution takes place quite readily, while with others it is neces- 
sary to boil some time. The wool is taken out, a slight excess 
of hydrochloric acid is added to the solution, another piece 

* Ztschr. anal. Chem., 35 (1896), 397. 



22 2 AIR, WATER, AND FOOD. 

of wool is immersed and again boiled. With vegetable coloring 
matter this second dyeing gives practically no color, and there 
is no danger of mistaking a fruit color for one of coal-tar origin. 

Notes. — It is absolutely necessary that the second dyeing 
should be made, as some of the coal-tar dyes will dye a dirty 
orange in the first acid bath which might be easily passed 
for vegetable color but on treatment in alkaline bath and 
second acid bath becomes a bright pink. 

Another advantage in the second dyeing is that if a large 
piece of woolen cloth is used in the first dyeing, and a small 
piece in the second dyeing, small amounts of coloring matter 
can be brought out much more decidedly in the second 
dyeing, where practically all of the vegetable coloring matter 
has been excluded. 

Several colors which are not coal-tar dyes, notably archil, 
archil derivatives, and sulphonated indigo, give reactions by 
this method and are liable to be confused with coal-tar colors. 
For hints as to the method for detecting these reference may 
be made to Bulletin 107, Bureau of Chemistry, page 190. 

Methods for the further separation and identification of 
the artificial colors cannot be taken up here for lack of space. 
The student is referred to Leach: "Food Inspection and 
Analysis," p. 628 et seq.\ Mulliken: " The Identification of 
Commercial Dyestuffs;" and a paper by Green, Yeoman, 
and Jones on " The Identification of Dyestuffs on A nimal Fibres."* 

Preservatives. — The preservatives most commonly em- 
ployed in wines are salicylic and benzoic acids. Sulphurous 
acid and sulphites are also used. For methods of detecting 
other substances less commonly employed, such as abrastol, 
beta-naphthol, etc., reference may be made to Bulletin 107 of 
the Bureau of Chemistry. Boric acid is occasionally used, 

* /. Soc. Dyers and Colourists, 1905, 236-243. 



food: analytical methods: fermented liquors. 223 

but since a small amount of it is normally present in wines, 
tests, to be of value, should be quantitative. 

Salicylic Acid. — Acidify about 50 c.c. of the wine with 
5 c.c. of dilute (1:3) sulphuric acid and extract in a separatory 
funnel with 25 c.c. of ether. Draw off the lower layer, wash 
the ether twice with water, using 10 c.c. each time and finally 
evaporate the ether in a porcelain dish at room temperature. 
To the residue in the dish add 2 to 3 drops of ferric alum solu- 
tion (p. 261). or very dilute ferric chloride. A deep purple 
or violet color indicates salicylic acid. 

Notes. — Not more than 50 c.c. should be used for the test, 
since a trace of salicylic acid seems normally present in some 
wines. 

The washing with water is to free the ether from traces of 
sulphuric acid which interferes w r ith the development of the 
violet color. 

Benzoic Acid* — Acidify about 100 c.c. of wine with sul- 
phuric acid, extract with ether, and evaporate the ethereal 
solution as in the detection of salicylic acid. Treat the resi- 
due with 2 or 3 c.c. of strong sulphuric acid. Heat till 
white fumes appear; organic matter is charred and benzoic 
acid is converted into sulpho-benzoic acid. A few crystals 
of ammonium nitrate are then added. This causes the for- 
mation of metadinitrobenzoic acid. When cool the acid is 
diluted with water and ammonia added in excess, followed 
by a drop or two of ammonium sulphide. The nitro-compound 
becomes converted into ammonium metadiamidobenzoic acid, 
which possesses a red color. This reaction takes place imme- 
diately, and is seen at the surface of the liquid without stirring. 

Sulphurous Acid and Sulphites.- — See directions under Beer, 
page 225. 

* Mohler: Bull. Soc. Chim. [3], 3, {1896) 414. 



224 AIR J WATER, AND FOOD. 

BEER AND OTHER MALT LIQUORS. 

Before analysis the sample must be thoroughly shaken in 
a large flask, in order to remove carbon dioxide. 

Specific Gravity. — Taken with a pyknometer or Sprengel 
tube at I5°.5 C. 

Alcohol. — Determined as in the analysis of wine. It will 
not be necessary to neutralize the free acid before distilling. 

Extract. — Determine the extract content corresponding 
to the specific gravity of the dealcoholized beer according to 
Table For this purpose employ the formula 

in which Sp is the specific gravity of the dealcoholized beer, 
g the specific gravity of the beer, and g f the specific gravity 
of the distillate obtained in the determination of alcohol. 
Instead of using this formula the residue from the distillation of 
alcohol is sometimes diluted to the original volume, and its 
specific gravity taken. This is often impracticable owing to 
the necessity of employing tannic acid to prevent foaming 
in the distilling flask, and owing to the coagulation of 
proteids during the distillation. 

Note. — The extract of beer cannot be accurately deter- 
mined by evaporation and drying at the boiling-point of 
water because of the dehydration of the maltose. 

Ash. — Evaporate 25 c.c. to diyness and determine as in 
the analysis of wine. 

Free Acids. — Heat 20 c.c. to incipient boiling to expel 

carbon dioxide and titrate as in the analysis of wine. Fixed 

acids, consisting principally of lactic and succinic, are calcu- 

N 
lated as lactic acid. One c.c. of — sodium hydroxide =0.0090 

gram of lactic acid. 



food: analytical methods: fermented liquors. 225, 

Reducing Sugar. — Dilute 25 c.c. of the beer, freed from 
carbon dioxide, to 100 c.c. Determine the reducing sugar in 
25 c.c. of this solution as directed on page 181, enough water 
being added to make the total volume of the Fehling's solution- 
sugar mixture 100 c.c. Express the results in terms of maltose, 
as given in Table XII. 

Preservatives. — The preservatives most commonly em- 
ployed in beer are benzoic and salicylic acids and their sodium 
salts, sulphites and fluorides. 

Benzoic and Salicylic Acids. — Detected as described under 
Wine. 

Sulphites. — Qualitative Test. — Use an apparatus similar to 
that described for the determination of volatile acids in wine. To 
50 c.c. of the sample add about a gram of sodium bicarbonate, 
20 c.c. of 20 per cent, phosphoric acid, and immediately con- 
nect the flask with the condenser. Pass steam through the 
flask until about 20 c.c. have collected in the distillate. To 
the distillate add bromine water in slight excess and boil. 
Expel the excess of bromine and test for sulphuric acid with 
hydrochloric acid and barium chloride in the usual manner. 

Notes. — The method described does not distinguish between 
free sulphurous acid and that present in the form of sulphites. 
The former can be distilled without the addition of phosphoric 
acid. 

The presence of sulphites in a sample should not be con- 
sidered evidence of added preservatives unless an excessive 
amount is found since the use of sulphured malt or hops may 
introduce a small amount. To obtain conclusive data a quan- 
titative determination of the amount present should be made. 
This can be done by a method very similar to that used for 
the detection, taking greater precautions against oxidation 
and absorbing the sulphurous acid in standard iodine solution. 
Care should be taken also to avoid the distillation of iodine- 



2 26 AIR, WATER, AND FOOD. 

reducing substances other than sulphurous acid. For a detailed 
discussion of the determination reference may be made to 
the following papers: Bureau of Chemistry, Bull. 107, p. 187; 
Gudeman: /. Ind. Eng. Chem., 1909, p. 81; Woodman and 
Gadsby: /. Ind. Eng. Chem., 1909. 

Fluorides. — The well-known qualitative test for fluorides by 
etching a glass plate may be modified by the use of a suitable 
condenser and made sufficiently delicate to be used here. It 
is possible also by suitable regulation of the temperature to 
make the test approximately quantitative.* 

FLAVORING EXTRACTS. 

The work on alcoholic liquids can be pleasantly varied by 
substituting for it in some cases the determination of alcohol 
and other important components of the usual flavoring essences, 
the most important of which are vanilla and lemon. Several 
important types of food methods, such as the determination 
of essential oils and quantitative extraction with volatile 
solvents, are also brought to the attention of the student. 

VANILLA. 

Vanilla extract is a dilute alcoholic tincture of the vanilla 
bean, the fruit of a climbing plant of the orchid family. The 
best grades are made by allowing the cut and bruised beans to 
macerate in the alcohol for several months, the liquid thus 
obtained being deep brown in color, with a delightful perfume 
and flavor. Sugar is added to assist in the extraction and to 
sweeten the product. 

The cost of a quart of the pure extract, according to Winton,f 

* Woodman and Talbot: J. Am. Chem. Soc, 1906, 1437; 1907, 1362. 
t Conn. Agr. Exp. Sta. Report, 1901, 150. 



food: analytical methods: flavoring extracts. 227 

is from about 60 cents to S2.50, depending chiefly upon the 
grade of beans used. 

The composition of five pure vanilla extracts, made from 
beans of different grades, is given in the following table, * the 
results being expressed in per cent, by weight: 



Grade of Bean. 



Specific 
Gravity. 



Vanillin. , Alcohol. 



Total 
Residue. 



Cane- 
sugar. 



Mexican (whole) 

Mexican (cut) 

South American (whole) 

Bourbon (whole) 

Tahiti (whole) 



1. 0159 
1. 0146 
1 .0109 
1 .0166 
1. 0104 



0.125 
0.065 
0.215 
0.138 
0.108 



37-96 
39-92 
38-58 
38.32 
38-84 



22.60 
23.10 
22.00 
23-13 

75 



21 



19.90 
19.20 
19.00 
20.40 
20.00 



The adulteration of vanilla extract consists principally in 
the use of extract of Tonka bean, a cheap substitute somewhat 
resembling vanilla in its flavor, in the use of artificial prepara- 
tions of the active principles of vanilla and tonka, vanillin and 
coumarin, and in the addition of artificial color, usually cara- 
mel. A cheap extract may be entirely an artificial mixture, 
made of artificial vanillin or coumarin, or both, in weak alcohol, 
colored with caramel. An occasional adulteration is the use 
of alkali, such as potassium bicarbonate, to hold the resin in 
solution and permit the use of a more dilute alcohol. 

Analytical Methods. — Alcohol. — Measure 25 c.c. of the 
sample, add 100 c.c. of water, and determine the alcohol by 
volume, as directed on page 217, omitting the use of sodium 
hydroxide or tannic acid. 

Vanillin and Coumarin. — (Method of Hess and Prescott, 
modified by Winton and Bailey. f) Weigh 25 grams into a 
200-C.C beaker with marks showing volumes of 25 and 50 c.c. 
Dilute to the 50-c.c. mark and evaporate in a water-bath to 

* Conn. Agr. Exp. Sta. Report, 1901, 150. 

f J. Am. Chem. Soc, 1905, 719; Bur. o/Chem., Bull. 107, 156. 



2 28 AIR, WATER, AND FOOD. 

25 c.c. at a temperature in the bath of not more than yo° C. 
Dilute a second time to 50 c.c. and evaporate to 25 c.c. Add 
neutral lead acetate solution drop by drop until no more pre- 
cipitate forms. Stir with a glass rod to facilitate flocculation 
of the precipitate, filter through a moistened filter, and wash 
three times with hot water, taking care that the total filtrate 
does not measure more than 50 c.c. Cool the filtrate and shake 
with 20 c.c. of ether in a separatory funnel. Remove the ether 
to another separatory funnel and repeat the shaking of the 
aqueous liquid with ether three times, using 15 c.c. each time. 
Shake the combined ether solutions four or five times with 2 
per cent, ammonium hydroxide, using 10 c.c. for the first 
shaking and 5 c.c. for each subsequent shaking. Set aside the 
combined ammoniacal solutions for the determination of 
vanillin. 

Wash the ether solution into a weighed dish and allow the 
ether to evaporate at the room temperature. Dry in a desic- 
cator, and weigh. Stir the residue for fifteen minutes with 
15 c.c. of petroleum ether (boiling-point 30 to 40 C.) and 
decant the clear liquid into a beaker. Repeat the extraction 
with petroleum ether two or three times. Allow the residue 
to stand in the air until apparently dry, completing the drying 
in a desiccator. Weigh, and deduct the weight from the weight 
of the residue obtained after the ether evaporation, thus obtain- 
ing the weight of the coumarin. 

Allow the petroleum ether extract to evaporate at room 

temperature. If it is coumarin it may be recognized by the 

characteristic odor, resembling that of "sweet grass," and by 

Leach's test * as follows: Dissolve the residue in a few drops of 

N 
hot water, and add one or two drops of — iodine in potassium 

* Leach: "Food Inspection and Analysis," 738. 



food: analytical methods: flavoring extracts. 229 

iodide. On stirring with a rod, a brown precipitate will form, 
which will gather into dark green flocks. The reaction is 
especially marked if carried out in a white porcelain crucible 
or dish. 

Slightly acidulate the ammoniacal solution reserved for 
vanillin with 10 per cent, hydrochloric acid. Cool, and shake 
out in a separatory funnel with four portions of ether, as 
described for the first ether extraction. Evaporate the ether 
at room temperature in a weighed dish, dry over sulphuric 
acid, and weigh the vanillin. 

If the residue is white it may be safely assumed in the 
majority of cases that it is pure vanillin. If dark colored, 
however, it should be purified as in the case of conmarin, and 
the percentage calculated from the loss in weight. 

Notes. — The separation of vanillin and coumarin is based 
on the differences in their chemical constitution. Vanillin is 
hydroxymethoxy benzoic aldehyde, while coumarin is the anhy- 
dride of orthohydroxycinnamic acid. On account of the 
aldehydic nature of the vanillin the separation by dilute ammo- 
nia is possible, the aldehyde ammonia compound of vanillin 
being readily soluble in water, while the coumarin remains 
wholly in the ether. 

Acetanilid has been reported in vanillin extracts, being 
present as an adulterant of the artificial vanillin employed, 
but its use is rare. If present, it will be found in the residue 
from the petroleum ether extraction and can be recognized by 
its melting-point, 11 2° C, and appropriate tests. 

Resins. — Evaporate 25 or 50 c.c. of the extract to one-third 
its volume on the water-bath in order to remove the alcohol. 
Make up to the original volume with hot water. If no alkali 
has been used in the manufacture of the extract, the resin 
should appear at this point as a flocculent brown residue. Add 
acetic acid in slight excess, allow the evaporating-dish to stand 



230 AIR, WATER, AND FOOD. 

in a warm place for a time to separate the resin completely, 
and filter. Wash the residue on the filter, and save both the 
filtrate and residue. Test the resin by placing pieces of the 
filter, with the resin attached, in a few cubic centimeters of dilute 
caustic potash. The resin is dissolved with a deep red color, 
and on acidifying is again precipitated. Test the filtrate by 
adding to it a few drops of basic lead acetate. A bulky pre- 
cipitate is formed, on account of the organic acid, gums, etc., 
present. 

Confirm the resin test by shaking 5 c.c. portions of the 
extract in separate test-tubes with 10 c.c. of amyl alcohol and 
10 c.c. of ether. With pure extracts the upper layers will be 
colored, varying from light yellow to deep brown; with artificial 
extracts, free from resin, the amyl alcohol and ether layers will 
be uncolored. 

Note. — While the artificial vanillin, as sold on the market 
and used in the manufacture of low-grade extracts, is identical 
with the vanillin of the vanilla bean, it is true that pure extracts 
owe their value and flavor to other ingredients as well as to the 
vanillin present. Among these " extractive matters" the resins 
are important from an analytical standpoint, serving by their 
presence or absence to determine whether true vanilla is present 
or the extract entirely artificial. As a quick and ready test, 
serving to distinguish artificial extracts from genuine prepara- 
tions of the vanilla bean, the amyl alcohol and ether tests will 
be found especially useful. 

Color: Caramel. — Caramel is the color commonly used in 
vanilla extracts, although coal-tar dyes have been found. The 
presence of dyes is sometimes indicated by the color of the 
amyl alcohol in testing for the resin, they being in many cases 
soluble in amyl alcohol, but insoluble in ether. The two tests 
for caramel which in the author's experience have proven most 
satisfactory are the lead acetate test and the paraldehyde test. 



food: analytical methods: flavoring extracts. 231 

Lead Acetate Test. — The coloring matter present in vanilla 
extracts is almost completely removed when the dealcoholized 
extract is treated with a few cubic centimeters of basic lead 
acetate solution. When caramel is present, the filtrate and 
precipitate, if any, have the characteristic red-brown color of 
caramel. 

Paraldehyde Test. — To 15 c.c. of the extract add 2 c.c. of 
zinc chloride (5 per cent, solution), and 2 c.c. of caustic potash 
(2 per cent, solution). Filter, wash the precipitate with hot 
water, and dissolve it in 15 c.c. of acetic acid (10 per cent, 
solution). Concentrate on the water-bath to one-half or one- 
third its volume, neutralize the excess of acid, and transfer the 
clear solution to a rather large test-tube. Add three volumes 
of paraldehyde and just enough alcohol to make the mixture 
homogeneous. If caramel is present a brown flocculent pre- 
cipitate will form on standing over night. 

Note. — The treatment with zinc hydroxide is to separate 
the caramel from sugar, which is present in many extracts, 
and interferes with the paraldehyde test.* The precipitate 
obtained with paraldehyde is probably caramel and not the 
product of a chemical reaction. 

LEMON. 

Lemon extract is usually made by dissolving oil of lemon, 
obtained by expression or distillation from the rind of the 
lemon, in strong alcohol. The product is sometimes colored 
with the color of lemon peel. The Federal standards f require 
a content of lemon oil of at least 5 per cent, by volume. The 
expensive ingredient of the extract is the alcohol, since alcohol 
of at least 80 per cent, strength by volume must be used to 
dissolve 5 per cent, of lemon oil; hence in making cheap extracts 

* Woodman and Newhall: Tech. Quart., 21, 280. 

\ U. S. Dept. Agric, Office of the Secretary, Circ. iq. 



232 AIR, WATER, AND FOOD. 

the manufacturer endeavors to use a dilute alcohol, even under 
the necessity of omitting a portion or all of the oil of lemon. 

The common forms of adulteration of lemon extract are the 
use of weak alcohol and consequent deficiency of lemon oil, 
as already noted; the substitution for the lemon oil of small 
amounts of stronger oils, as oil of citronella, oil of lemon-grass, 
and the like; the use of citral, the odorous principle of lemon 
oil, used for making the so-called "terpeneless lemon extracts;" 
and the coloring of the extracts by coal-tar colors or turmeric. 

Preliminary Test. — To a little of the extract in a test-tube 
add seven or eight times its volume of water. A high-grade 
extract will show a heavy cloud, due to the precipitation of the 
lemon oil. If no cloudiness or turbidity appears it may be 
safely inferred that no oil is present. 

Alcohol. — The determination of alcohol is somewhat com- 
plicated in this case by the presence of the volatile oil of lemon 
which must be removed before distilling. 

Dilute 20 c.c. of the extract to 100 ex. with water, and 
pour the mixture into a dry Erlenmeyer flask containing 5 grams 
of light magnesium carbonate. Shake thoroughly and filter 
through a dry filter. Measure 50 c.c. of the clear filtrate, add 
about 15 c.c. of water, and distil 50 c.c, as directed on page 217. 
From the specific gravity of the distillate determine the per cent, 
of alcohol by volume, and this, multiplied by 5, will give the 
percentage in the original extract. 

Note. — The magnesia serves to absorb the precipitated 
oil and prevent it from passing through the filter. 

Lemon Oil. — Pipette 20 c.c. of the extract into a Babcock 
milk bottle; add 1 c.c. dilute hydrochloric acid (1:1); then 
add from 25 to 28 c.c. of water previously warmed to 6o° C; 
mix and let stand in water at 6o° for five minutes; whirl in 
centrifuge for five minutes; fill with warm water to bring the 
oil into the graduated neck of the flask; repeat whirling for 



food: analytical methods: flavoring extracts. 233 

two minutes; stand the flask in water at 6o° C. for a few minutes 
and read the per cent, of oil by volume. If the determination 
is not made in duplicate the flask should be balanced by another 
containing an equal weight of water. In case oil of lemon is 
present in amounts over 2 per cent, add to the percentage of 
oil found 0.4 per cent, to correct for the oil retained in solution. 
If less than 2 per cent, and more than 1 per cent, is present, 
add 0.3 per cent, for correction. 

Refractive Index of the Oil. — With a narrow glass tube 
remove a few drops of the oil obtained in the neck of the Babcock 
flask in the previous determination and determine its index 
of refraction at 25 °, using the Abbe refractometer. The read- 
ing for pure lemon oil at 25 is 1 .4715-1 .4740. Most of the 
adulterants give a higher refractive index; oil of turpentine 
is distinctly lower. 

Color. — Test for coal-tar colors by evaporating a portion of 
the extract to dryness on the water-bath. Dissolve the residue 
in water and carry out the double dyeing method, as described 
on page 221. 

To test for turmeric add to a portion of the sample three 
drops of saturated boric acid solution, one small drop of dilute 
(1:10) hydrochloric acid, and a piece of filter-paper so arranged 
that it is only half immersed in the liquid. Evaporate to 
dryness on the water-bath. In the presence of turmeric the 
paper will be colored pink and the test may be confirmed as 
described on page 188, Excess of hydrochloric acid should be 
avoided, as in testing for boric acid. 

Citral. — See /. Am. Chem. Soc. y 1906, 1472. 



APPENDICES. 



APPENDIX A. 



Table I. 

TENSION OF AQUEOUS VAPOR IN MILLIMETERS OF MERCURY FROM 
0° TO 30°. 9 C, REDUCED TO 0° AND SEA-LEVEL. 





o°.o. 


o°.i. 


O .2. 


o°3- 


o°. 4 . 


o°. 5 . 


o°.6. 


o°. 7 . 


o°.8. 


o°. 9 . 


o° 


4-57 


4.60 


4.64 


4.67 


4- 70 


4-74 


4-77 


4.80 


4.84 


4.87 


I 


4.91 


4.94 


4.98 


5.02 


5.05 


5 -09 


5-12 


5.16 


5-20 


5.23 


2 


5.27 


5.31 


5-35 


5-39 


5-42 


5-46 


5.5o 


5-54 


5-58 


5.62 


3 


5-66 


5.70 


5-74 


5-78 


5-82 


5-86 


5-90 


5-94 


5-99 


6.03 


4 


6.07 


6. 11 


6.15 


6.20 


6.24 


6.28 


6-33 


6-37 


6.42 


6.46 


5 


6.51 


6-55 


6.60 


6.64 


6.69 


6-74 


6.78 


6.83 


6.88 


6.92 


6 


6.97 


7.02 


7.07 


7.12 


7.17 


7.22 


7.26 


7-31 


7.36 


7.42 


7 


7-47 


7-52 


7-57 


7.62 


7-67 


7-72 


7.78 


7.83 


7.88 


7-94 


8 


7-99 


8.05 


8.10 


8.15 


8.21 


8.27 


8.32 


8.38 


8-43 


8-49 


9 


8.55 


8.61 


8.66 


8.72 


8.78 


8.84 


8.90 


8.96 


9.02 


9.08 


10 


9.14 


9.20 


9.26 


9-32 


9-39 


9-45 


9-5i 


9.58 


9.64 


9.70 


11 


9-77 


9-33 


9.90 


9.96 


10.03 


10.09 


10.16 


10.23 


10.30 


10.36 


12 


10.43 


10.50 


io.57 


10.64 


10.71 


10.78 


10.85 


10.92 


10.99 


11.06 


13 


11. 14 


11. 21 


11.28 


11.36 


H-43 


11 .50 


11.58 


11.66 


H-73 


11. 81 


14 


11.88 


11.96 


12.04 


12. 12 


12.19 


12.27 


12-35 


12.43 


12.51 


12.59 


15 


12.67 


12.76 


12.84 


12.92 


13.00 


13.09 


13.17 


!3-25 


13-34 


13.42 


16 


I35I 


13-60 


13.68 


13-77 


13.86 


13-95 


14.04 


14.12 


14.21 


14.30 


17 


14.40 


14.49 


14.58 


14.67 


14.76 


14.86 


14-95 


15.04 


15.14 


1523 


18 


15-33 


15-43 


15-52 


15-62 


15.72 


15.82 


15-92 


16.02 


16.12 


16.22 


19 


16.32 


16.42 


16.52 


16.63 


16.73 


16.83 


16.94 


17.04 


17.15 


17.26 


20 


I7-36 


17-47 


17-58 


17.69 


17.80 


17.91 


18.02 


18.13 


18.24 


18.35 


21 


18.47 


18.58 


18.69 


18.81 


18.92 


19.04 


19.16 


19.27 


19-39 


19-51 


22 


19.63 


19-75 


19.87 


19.99 


20.11 


20.24 


20.36 


20.48 


20.61 


20.73 


23 


20.86 


20.98 


21. 11 


21 .24 


21-37 


21. 50 


21.63 


21.76 


21.89 


22.02 


24 


22.15 


22.29 


22.42 


22.55 


22.69 


22.83 


22.96 


23. 10 


23-24 


23.38 


25 


23.52 


23.66 


23.80 


23-94 


24.08 


24.23 


24-37 


24.52 


24.66 


24.81 


26 


24.96 


25-10 


25.25 


25.40 


25-55 


25.70 


25.86 


26.01 


26.16 


26.32 


27 


26.47 


26.63 


26.78 


26.94 


27. 10 


27.26 


27.42 


27.58 


27-74 


27.90 


28 


28.07 


28.23 


28.39 


28.56 


28.73 


28.89 


29.06 


29.23 


29.40 


29- 57 


29 


29.74 


29.92 


30.09 


30.26 


30.44 


30.62 


30.79 


30.97 


31-15 


31.33 


30 


3I-5I 


31.69 


31.87 


32.06 


32.24 


32-43 


32.61 


32.80 


32.99 


33.18 



236 



APPENDIX A. 



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APPENDIX A. 



239 











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240 



APPENDIX A. 



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APPENDIX A. 



24X 





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242 



APPENDIX A. 
Table VII. 



TABLE OF HARDNESS, SHOWING THE PARTS OF CALCIUM CAR- 
BONATE (CaC0 3 ) IN 1,000,000 FOR EACH TENTH OF A CUBIC 
CENTIMETER OF SOAP SOLUTION USED. 





0.0 


O.I 


0.2 


0.3 


0.4 


0.5 


0.6 


0.7 


0.8 


0.9 




cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


0.0 
















O.O 


1.6 


3-2 


1 .0 


4.8 


6.3 


7-9 


9-5 


II. I 


12.7 


14-3 


15-6 


16.9 


18.2 


2.0 


19-5 


20.8 


22.1 


23.4 


24.7 


26.O 


27-3 


28.6 


29.9 


31-2 


30 


32.5 


33-8 


35-1 


36.4 


37-7 


39 


40- 3 


41.6 


42.9 


44-3 


4.0 


45 -7 


47.1 


48.6 


50.0 


51.4 


52.9 


54.3 


55-7 


57-1 


58.6 


5-o 


60.0 


61.4 


62.9 


64-3 


65.7 


67.1 


68.6 


70.0 


71.4 


72.9 


6.0 


74-3 


75-7 


77-1 


78.6 


80.O 


81.4 


82.9 


84-3 


85-7 


87.1 


7.0 


88.6 


90.0 


91.4 


92.9 


94-3 


95-7 


97.1 


98.6 


100. 


101.5 


8.0 


103.0 


104.5 


106.0 


1075 


IOg.O 


no. 5 


112. 


II3-5 


1150 


116. 5 


9.0 


118.0 


"9-5 


Z2I.I 


122.6 


124. 1 


125.6 


127. 1 


128.6 


130. 1 


131-6 


10. 


133-1 


134.6 


I36. I 


137-6 


I39-I 


140.6 


142. 1 


143-7 


145-2 


146.8 


11 .0 


148 4 


150 


151. 6 


153-2 


154-8 


156.3 


157-9 


159-5 


161. 1 


162.7 


12.0 


164.3 


165.9 


I67-5 


169.0 


170.6 


172.2 


173-8 


175.4 


177-0 


178.6 


13.0 


180.2 


181. 7 


183.3 


184.9 


186.5 


188. 1 


189.7 


I9I-3 


192.9 


194.4 


14.0 


196.0 


197.6 


199.2 


200.8 


202.4 


204.0 


205.6 


207.1 


208.7 


210.3 


15-0 


211. 9 


213-5 


215. 1 


216.8 


218.5 


220.2 


221.8 


223.5 


225.2 


226.9 



Table VIII. 

SHOWING THE NUMBER OF CUBIC CENTIMETERS OF OXYGEN DIS- 
SOLVED IN IOOO CUBIC CENTIMETERS OF WATER WHEN 
SATURATED AT DIFFERENT TEMPERATURES, AS CAL- 
CULATED BY WINKLER.' 



* 



Deg. Cent. 


Cu. Cm. 


Deg. Cent. 


Cu. Cm. 


Deg. Cent. 


Cu. Cm. 


O 


IO.187 


II 


7.692 


21 


6.233 


I 


9.910 


12 


7.518 


22 


6. 114 


2 


9-643 


13 


7-352 


23 


5.999 


3 


9-387 


14 


7.192 


24 


5.886 


4 


9.142 


15 


7.038 


25 


5 • 776 


5 


8.907 


16 


6.891 


26 


5-669 


6 


8.682 


17 


6.750 


27 


5 • 564 


7 


8.467 


18 


6.614 


28 


5.460 


8 


8.260 


19 


6.482 


29 


5.357 


9 


8.063 


20 


6.356 


30 


5.255 


10 


7.873 











* Berichte, 22 (1889), 1772. 



APPENDIX A. 



243 



Table IX. 

FOR CORRECTING THE SPECIFIC GRAVITY OF MILK ACCORDING TO 
TEMPERATURE. ADAPTED FROM THE TABLE OF VIETH. 

(Temperature in Degrees Centigrade.) 



Specific 
Gravity. 



I.025 
26 

27 
28 
29 
30 
31 
32 
33 
34 
35 



24.1 
25- 1 

26.1 
27.0 
2S.0 
29.0 
29.9 

30.9 
31.8 

32.7 
33-6 



24-3 
25.2 
26.2 
27.2 

28.2 
29. 1 
30. 1 

3i-i 
32.0 
33-o 
33-9 



24 
25 

20 

27 

28 

29 

30 

31-3 

32.3 

33-2 

34-i 



J-.O 


- 


24.6 


24.7 


25-5 


25-7 


26.5 


26.7 


27.5 


27.7 


28.5 


28.7 


29-5 


29 -7j 


30.4 


30.6 


31-4 


3 1 - ! 


32.4 


32.6 


33-4 


33-6 


34-4 


34-6 



24.9 

25.9, 
26.9: 

27. 9I 
2S.9 
29.9 

30.9 

3i-9 
32-9 
33-9 
34-9 



25.1 
26. 1 

27.1 

28.1 

29 

30 

3i 

32 

33 

34 



35-2 



37 


18 


25-3 


25-4 


26.3 


26.5 


27.4 


27-5 


28.4 


28.5 


29.4 


29-5 


30.4 


30.5 


3i-4 


31.5 


32.4 


32.6 


33-4 


33-6 


34-4 


34-6 


35-4 


35-o 



25.6 
26.7 

27-7 
28.7; 
29.8 
30.8 
3i-8| 
32-9 
33-9 

34-9: 

35-9 



25 
27 
28 

29 

30 

3i 

32.2 

33-2 

34-2 

35-2 

36.2 



Directions. — Find the observed gravity in the left-hand column. Then 
in the same line, and under the observed temperature, will be found the 
corrected reading. 



244 



APPENDIX A. 



Table X. 



PERCENTAGE OF ALCOHOL 

i5°.5 c 



FROM THE SPECIFIC 
(HEHNER.) 



GRAVITY AT 





Percent 


Per cent 




Per cent 


Per cent 




Per cent 


Per cent 


Sp. Gr. 


Alcohol 


Alcohol 


Sp. Gr. 


Alcohol 


Alcohol 


Sp. Gr. 


Alcohol 


Alcohol 


i5°-5C. 


by 


by 


is°.sc. 


by 


by 


iS°.5 C. 


bv 


by 




Weight. 


Volume. 




Weight. 


Volume. 




Weight. 


Volume. 


I.OOOO 


0.00 


O.OO 














0.9999 


0.05 


O.07 


0.9959 


2-33 


2-93 


O.9919 


4.69 


5-86 


8 


O.II 


0.13 


8 


2-39 


3.00 


8 


4-75 


5-94 


7 


0.16 


0. 20 


7 


2.44 


3-°7 


7 


4.81 


6.02 


6 


O. 21 


0.26 


6 


2.50 


3-i4 


6 


4-87 


6.10 


5 


O. 26 


°-33 


5 


2.56 


3.21 


5 


4-94 


6.17 


4 


O.32 


0.40 


4 


2.61 


3.28 


4 


5.00 


6.24 


3 


0-37 


0.46 


3 


2.67 


3-35 


3 


5.06 


6.32 


2 


O.42 


o-53 


2 


2.72 


3-42 


2 


5-12 


6.40 


I 


O.47 


0.60 


1 


2.78 


3-49 


1 


5-i9 


6.48 


O 


0-53 


0.66 





2.83 


3-55 





5-25 


6-55 


O.9989 


0.58 


0-73 


0.9949 


2.89 


3-62 


0.9909 


5-3i 


6.63 


8 


O.63 


0.79 


8 


2.94 


3- 6 9 


8 


5-37 


6.71 


7 


O.68 


0.86 


7 


3.00 


3-76 


7 


5-44 


6.78 


6 


O.74 


°-93 


6 


3.06 


3-83 


6 


5-5o 


6.86 


5 


O.79 


0.99 


5 


3.12 


3-9° 


5 


5-56 


6-94 


4 


O.84 


1.06 


4 


3-i8 


3-98 


4 


5.62 


7.01 


3 


O.89 


1-13 


3 


3-24 


4-o5 


3 


5-69 


7.09 


2 


0-95 


1. 19 


2 


3-29 


4.12 


2 


5-75 


7.17 


1 


I. OO 


1. 26 


1 


3-35 


4.20 


1 


5-8i 


7-25 





I.06 


i-34 





3-4i 


4.27 





5-87 


7-32 


0.9979 


I. 12 


1.42 


0-9939 


3-47 


4-34 


0.9899 


5-94 


7.40 


8 


1. 19 


i-49 


8 


3-53 


4-42 


8 


6.00 


7-48 


7 


1-25 


i-57 


7 


3-59 


4-49 


7 


6.07 


7-57 


6 


I. 31 


1-65 


6 


3-65 


4-5° 


6 


6.14 


7.66 


5 


i-37 


i-73 


5 


3-7i 


4-63 


5 


6.21 


7-74 


4 


1-44 


1. 81 


4 


3-76 


4.71 


4 


6.28 


7-83 


3 


1.50 


1.88 


3 


3.82 


4-78 


3 


6.36 


7.92 


2 


1-56 


1.96 


2 


3-88 


4-85 


2 


6-43 


8.01 


1 


1.62 


2.04 


1 


3-94 


4-93 


1 


6.50 


8.10 





1-69 


2.12 





4.00 


5.00 





6-57 


8.18 


0.9969 


1-75 


2.20 


0.9929 


4.06 


5-o8 


0.9889 


6.64 


8.27 


8 


1. 81 


2.27 


8 


4.12 


5-i6 


8 


6.71 


8.36 


7 


1.87 


2-35 


7 


4.19 


5-24 


7 


6.78 


8-45 


6 


i-94 


2-43 


6 


4-25 


5-32 


6 


6.86 


8-54 


5 


2.00 


2-51 


5 


4-3 1 


5-39 


5 


6 -93 


8.63 


4 


2.06 


2.58 


4 


4-37 


5-47 


4 


7.00 


8.72 


3 


2. 11 


2.62 


3 


4-44 


5-55 


3 


7.07 


8.80 


2 


2.17 


2.72 


2 


4-5° 


5-63 


2 


7-i3 


8.88 


1 


2. 22 


2-79 


1 


4-56 


5-7i 


1 


7.20 


8.96 





2.28 


2.86 





4.62 


5-78 





7.27 


9.04 



APPENDIX A. 



245 



Table X. — Continued. 

PERCENTAGE OF ALCOHOL. 





Per cent 


Per cent 




Per cent 


Per cent 




! Per cent 


Per cent 


Sp. Gr. 


Alcohol 


Alcohol 


Sp. Gr. 


Alcohol 


Alcohol 


Sp. Gr. 


! Alcohol 


Alcohol 


i5°.S C. 


by 


by 


I5°.SC. 


by 


by 


I5°-SC. 


! by 


by 




Weight. 


Volume. 




1 Weight. 


Volume. 




i Weight. 


Volume. 


O.9879 


7-33 


9-13 


4 


10.54 


i3-°5 


O.9789 


14.OO 


17.26 


8 


7.40 


9. 21 


3 


10.62 


13-15 


8 


14.09 


17.37 


7 


7-47 


9.29 


2 


10.69 


l3- 2 4 


7 


14.18 


17.48 


6 


7-53 


9-37 


1 


10.77 


13-34 


6 


14.27 


17-59 


5 


7.60 


9-45 





10.85 


J3-43 


5 


I4-3 6 


17.70 


4 


7.67 


9-54 








4 


14-45 


17.81 


3 


7-73 


9.62 


0.9829 


IO.92 


13-52 


3 


14-55 


17.92 


2 


7.80 


9.70 


8 


11 .00 


13.62 


2 


14.64 


18.03 


1 


7-87 


9-78 


7 


11.08 


13-72 


1 


J 4-73 


18.14 





7-93 


9.86 


6 

5 


11. 15 
11.23 


13.81 
!3-9° 





14.82 


18.25 


0.9869 


8.00 


9-95 


4 


11. 31 


*3-99 


0.9779 


14.90 


18.36 


8 


8.07 


10.03 


3 


11.38 


14.09 


8 


15.00 


18.48 


7 


8.14 


10.12 


2 


11.46 


14.18 


7 


15.08 


18-58 


6 


8.21 


10.21 


1 


n-54 


14.27 


6 


I5-I7 


18.68 


5 


8.29 


10.30 





11.62 


J 4-37 


5 


15-25 


18.78 


4 


8.36 


10.38 








4 


15-33 


18.88 


3 


8-43 


10.47 


0.9819 


II.69 


14.46 


3 


15-42 


18.98 


2 


8.50 


10.56 


8 


11.77 


14.56 


2 


i5-5o 


19.08 


1 


8-57 


10.65 


7 


11.85 


14-65 


1 


15-58 


19.18 





8.64 


IO -73 


6 

5 


11.92 
12.00 


14.74 
14.84 





15-67 


19.28 
| 


0.9859 


8-71 


10.82 


4 


12.08 


14-93 


0.9769 


15-75 


19.39 


8 


8-79 


10.91 


3 


12.15 


15.02 


8 


15.83 


19.49 


7 


8.86 


11.00 


2 


12.23 


15.12 


7 


15-92 


19-59 


6 


8-93 


11.08 


1 


12.31 


15.21 


6 


16.00 


19.68 


5 


9.00 


11. 17 





12.38 


15-30 


5 


16.08 


19.78 


4 


9.07 


11.26 








4 


16.15 


19.87 


3 


9.14 


ii-35 


0.9809 


12.46 


I5-40 


3 


16.23 


19.96 


2 


9. 21 


11.44 


8 


12.54 


15-49 


2 


16.31 


20.06 


1 


9.29 


11.52 


7 


12.62 


15.58 


1 


16.38 


20.15 





9-36 


11. 61 


6 

5 


12.69 
12.77 


15.68 
15-77 





16.46 


20.24 


0.9849 


943 


11.70 


4 


12.85 


15-86 


0-9759 


16.54 


20.33 


8 


9-5o 


11.79 


3 


12.92 


15.96 


8 


16.62 


20.43 


7 


9-57 


11.87 


2 


13.00 


16.05 


7 


16.69 


20.52 


6 


9.64 


11.96 


1 


13.08 


16.15 


6 


16.77 


20.61 


5 


9.71 


12.05 





13-15 


16.24 


5 


16.85 


20.71 


4 


9-79 


12.13 








4 


16.92 


20.80 


3 


9.86 


12.22 


0.9799 


13-23 


16.33 


3 


17.00 


20.89 


2 


9-93 


12.31 


8 


13-31 


16.43 


2 


17.08 


20.99 


1 


10.00 


12.40 


7 


13-38 


16.52 


1 


17.17 


21.09 





10.08 


12.49 


6 

5 


13.46 
13-54 


16.61 
16.70 





17.25 


21.19 


0. 0839 


10.15 


12.58 


4 


13.62 


16.80 


0.9749 


17-33 


21.29 


8 


10.23 


12.68 


3 


13.69 


16.89 


8 


17.42 


20.39 


7 


10.31 


12.77 


2 


13-77 


16.98 


7 


i7-5o 


21.49 


6 


10.38 


12.87 


1 


13.85 


17.08 


6 


17.58 


21-59 


5 


10.46 


12.96 





13.92 


17.17 


5 


17.67 


21.69 



246 



APPENDIX A. 

Table X. — Continued. 

PERCENTAGE OF ALCOHOL. 





Per cent 


Per cent 


1 


Per cent 


Per cent 




Per cent 


Per cent 


Sp. Gr. 


Alcohol 


Alcohol 


Sp. Gr. 


Alcohol 


Alcohol 


Sp. Gr. 


Alcohol 


Alcohol 


I5°.5C. 


by 


by 


is°-sc. 


by 


by 


I5°.SC. 


by 


by 




Weight. 


Volume. 




Weight. 


"Volume. 




Weight. 


Volume. 


4 


17-75 


21.79 


4 


20.17 


24.68 


4 


22.54 


27.49 


3 


17-83 


21.89 


3 


20.25 


24.78 


3 


22.62 


27-59 


2 


17.92 


21.99 


2 


20.33 


24.88 


2 


22.69 


27.68 


I 


18.00 


22.09 


1 


20.42 


24.98 


1 


22.77 


27.77 


O 


18.08 


22.18 





20.50 


25.07 





22.85 


27.86 


0.9739 


18.15 


22. 27 


0.9709 


20.58 


25.17 


0.9679 


22.92 , 


27-95 


8 


18.23 


22.36 


8 


20.67 


25.27 


8 


23.00 


28.04 


7 


18.31 


22.46 


7 


20-75 


25.37 


7 


23.08 


28.13 


6 


18.38 


22-55 


6 


20.83 


25-47 


6 


23-15 


28.22 


5 


18.46 


22.64 


5 


20 92 


25-57 


5 


23.23 


28.31 


4 


18.54 


22,73 


4 


2I.OO 


25-67 


4 


23-31 


28.41 


3 


18.62 


22.82 


3 


21.08 


25 76 


3 


23.38 


28.50 


2 


18.69 


22.92 


2 


21.15 


25.86 


2 


23.46 


28-59 


1 


18.77 


23 OI 


1 


21.23 


25.95 


1 


23-54 


28.68 





18.85 


23.IO 





21.31 


26.04 





23.62 


28.77 


O.9729 


18 92 


23.19 


0.9699 


21.38 


26.13 


0.9669 


23.69 


28.86 


8 


19 00 


23-28 


8 


21.46 


26 22 


8 


2 3-77 


28.95 


7 


19.08 


23-38 


7 


21-54 


26.3I 


7 


23.85 


29.04 


6 


19 17 


23-48 


6 


21.62 


26.4O 


6 


23.92 


29-13 


5 


l9- 2 5 


23 58 


5 


21.69 


26.49 


5 


24.00 


29.22 


4 


19-33 


23.68 


4 


21.77 


26.58 


4 


24.08 


29.31 


3 


19.42 


23-78 


3 


21.85 


26.67 


3 


24-15 


29.40 


2 


I9-50 


23-88 


2 


21.92 


26.77 


2 


24-23 


29-49 


1 


19.58 


23.98 


1 


22.00 


26.86 


1 


24. 3 1 


29.58 





19.67 


24.08 





22.08 


26.95 





24.38 


29.67 


0.9719 


19-75 


24. l8 


0.9689 


22.15 


27.04 


0.9659 


24.46 


29.76 


8 


19.83 


24.28 


8 


22.23 


27- J 3 


8 


24-54 


29.86 


7 


19.92 


24-38 


7 


22.31 


27.22 


7 


24.62 


29-95 


6 


20.00 


24.48 


6 


22.38 


27-31 


6 


24.69 


30.04 


5 


20 08 


24.58 


5 


22.46 


27.40 


5 
4 

3 
2 


24-77 
24-85 
24.92 
25.00 


30.22 
30.40 



APPENDIX A. 



247 



Table XL 

EXTRACT IN WINE. 

Per Cent by Weight. 
[According to Windisch.] 



Sp. Gr. 


Ex- 


Sp. Gr. 


Ex- 


Sp. Gr. 


Ex- 


1 

'Sp. Gr. 


Ex- 


Sp. Gr. 


Ex- 


Sp. Gr 


Ex- 




tract. 




tract. 




tract. 




tract. 




tract. 




tract. 


1 . 0000 


0.00 


1 .0200 


5-17 


1 .0400 


10.35 


1 .0600 


15.55 


1 .0800 


20.78 


1 . 1 00a 


26 .04 


1 .0005 


0.13 


1.0205 


5.30 


1 .0405 


10.48 


1 .0605 


15.68 


1 .0805 


20.91 


1 . 1005 


26. 17 


1 .0010 


0.26 


1 .0210 


5-43 


1 .0410 


10.61 


1 .0610 


15.81 


1. 0810 


21 .04 


1 . IOIO 


26.30 


1 .0015 


0.39 


1 .0215 


5.56 


1-0415 


10.74 


1 .0615 


15-94 


1. 0815 


21.17 


1. 1015 


26.43 


r .0020 


0.52 


1 .0220 


5.69 


1 .0420 


10.87 


1 .0620 


16.07 


1 .0820 


21.31 


1 . 1020 


26.56 


1 .0025 


0.64 


1 .0225 


5-82 


1 .0425 


1 1 . 00 


1 .0625 


16.21 


1 .0825 


21.44 


1 .1025 


26.70 


1 .0030 


0.77 


1.0230 


5-94 


1.0430 


11 . 13 


1.0630 


16.33 


1 .0830 


21.57 


1 . 1030 


26.83 


1 -0035 


0.90 


10235 


6.07 


1 -0435 


11.26 


1-0635 


16.47 


1.0835 


21 . 70 


1 -1035 


26 . 96 


1 .0040 


1 °3 


1 .0240 


6. 20 


1 .0440 


n.39 


1 .0640 


16.60 


1 .0840 


21.83 


1 . 1040 


27.09 


1. 0045 


1. 16 


1.0245 


6.33 


1.0445 


11 .52 


1 0645 


16.73 


1.0845 


21 .96 


1. 1045 


27.22 


1 .0050 


1.29 


1 .0250 


6.46 


1.0450 


11 .65 


1 .0650 


16.86 


1 .0850 


22 .09 


1. 1050 


27.35 


1.0055 


1.42 


1-0255 


6.59 


1.0455 


11.78 


1-0655 


16.99 


1-0855 


22 . 22 


i- 1055 


27.49 


1 .0060 


1. 55 


1 .0260 


6.72 


1 .0460 


11. 91 


1 .0660 


17.12 


1 .0860 


22 .36 


1 . 1060 


27.62 


1 .0065 


1.68 


1.0265 


6.8s 


1 .0465 


13 .04 


1 .0665 


17.25 


1.0865 


22.49 


1 . 1065 


27.75 


1 .0070 


1. 81 


1 .0270 


6.98 


1.0470 


12.17 


1 .0670 


17.38 


1 .0870 


22 . 62 


1 . 1070 


27.88 


1.0075 


1.94 


1.0275 


7. 11 


1 -0475 


12 .30 


1.0675 


17-51 


1.0875 


22.75 


1. 1075 


28.01 


1 .0080 


2.07 


1 .0280 


7.24 


1 .0480 


12.43 


1.0680 


17.64 


1.0880 


22.88 


1 . 1080 


28.15 


1 .0085 


2.19 


1.0285 


7-37 


1 .0485 


12.56 


1.0685 


17.77 


1.0885 


23.OI 


1. 1085 


28.28 


1 .0090 


2.32 


1 .0290 


7- SO 


1 .0490 


12 .69 


1 .0690 


17 .90 


1 .0890 


23.I4 


1 . 1090 


28.41 


1.0095 


2-45 


1 .0295 


7.63 


I.Q495 


12.82 


1 .0695 


18.03 


1.0895 


23.28 


1. 1095 


28.54 


1 .0100 


2.58 


1 .0300 


7.76 


1 .0500 


12.95 


1 .0700 


18.16 


1 .0900 


23 .41 


1 . 1 100 


26 .67 


1 .0105 


2.71 


1.0305 


7.89 


1 -0505 


I3.08 


1.0705 


18.30 


1 .0905 


23.54 


1 . 1105 


28.81 


1 .0110 


2.84 


1 .0310 


8.02 


1 .0510 


13-21 


1 .0710 


18.43 


1 .0910 


23.67 


I . IIIO 


28.94 


1.0115 


2.97 


1-0315 


8.14 


1-0515 


13-34 


1 -0715 


18.56 


1. 0915 


23.80 


I . 1115 


29.07 


1 .0120 


3- 10 


1 .0320 


8.27 


1.0520 


13-47 


1 .0720 


18.69 


1 .0920 


23.93 


I . II20 


29.20 


1. 0125 


3-23 


1-0325 


8.40 


1-0525 


I3.6o 


1 .0725 


18.82 


1 .0925 


24.07 


I . 1125 


29-33 


1. 0130 


3.36 


1.0330 


8-53 


1.0530 


13-73 


1 .0730 


18.95 


1.0930 


24.20 


I.II30 


29.47 


1.0135 


3-49 


I-0335 


8.66 


1. 053S 


13-86 


I-0735 


19.08 


1 -0935 


24.33 


r."35 


29. 60 


1 .0140 


3-02 


1 .0340 


8.79 


1 . 0540 


13 -99 


1 .0740 


19.21 


1 .0940 


24.46 


1 . 1 1 40 


2973 


1. 0145 


3-75 


I-0345 


8.92 


I-054S 


14. 12 


1.0745 


19.34 


I.Q945 


24.59 


1. "45 


29.86 


1. 0150 


3.87 


1.0350 


9.05 


1.0550 


14-25 


1.0750 


19-47 


1 .0950 


24.72 


1.1150 


29.99. 


1.015s 


4.00 


I-0355 


9.18 


I-0555 


14.38 


I-0755 


19.60 


1 -0955 


24.85 


1. "55 


30.13 


1 .0160 


4.13 


1.0360 


9.3i 


1 .0560 


14.51 


1 .0760 


19-73 


1 .0960 


24.99 






1.016s 


4. 26 


1-0365 


9-44 


1.0565 


14.64 


1.0765 


19.86 


1 .0965 


25.12 






1. 0170 


4-39 


1.0370 


9-57 


1.0570 


M-77 


1.0770 


20.00 


1 .0970 


25-25 






1. 017s 


4.52 


I-0375 


970 


I.0575 


14.90 


1 -0775 


20. 12 


1 -0975 


25.38 






1 .0180 


4.65 


1 .0380 


9.83 


1 .0580 


15-03 


1 .0780 


20. 26 


1 .0980 


25-51 






1. 0185 


4.78 


1-0385 


9.96 


1.0585 


15.16 


1.0785 


20.39 


1 .0985 


25.64 






1 .0190 


4.91 


1 .0390 


10.09 


1 .0590 


15-29 


1 .0790 


20. 52 


1 .0990 


25.78 






1. 0195 


5-04 


1 -0395 


10. 22 


1 .0595 


15.42 


1.0795 


20.65 


I-Q995 


25.91 




. 



248 



APPENDIX A. 



Table XII. 

TABLE FOR REDUCING SUGAR CONDENSED 
MUNSON AND WALKER. 
(Expressed in milligrams.) 



FROM THAT OF 









O 










O 








u 


X 




CD 




u 


X 




p 3 

6 


«5 


u 

<D 

Q 


M 
M 
u 

> 

C 


+ 

A 

BX 

s 

< 


O 
aT S3 


O - 

2 ^ 
u 


6 

en 

2 
Q 


a 
bo 

to 

u 

CD 
> 

C 


+ 

A 

2X 
jc5 


O 

1)8 

ISO 

9 


10 


4.0 


4-5 


4.0 


5-9 


260 


117 .6 


121. 4 


176.3 


203.9 


is 


6.2 


6-7 


7-5 


9-9 


265 


120.0 


123.9 


179-7 


207.9 


20 


8.3 


8-9 


10.9 


13-8 


270 


122.5 


126. 4 


183.2 


211. 8 


25 


10.5 


11 . 2 


14.4 


17.8 


275 


124.9 


I28.9 


186.6 


215.8 


30 


12.6 


13-4 


17.8 


21.8 


280 


127.3 


I3I-4 


190. I 


219.7 


35 


14.8 


15.6 


21.3 


25-7 


285 


129.8 


133-9 


193-5 


223.7 


40 


16.9 


17.8 


24.7 


29.7 


290 


132.3 


I36.4 


196.9 


227.6 


45 


19. 1 


20. 1 


28.2 


33-7 


295 


134-7 


138.9 


200. 4 


231.6 


SO 


21.3 


22.3 


31-6 


37-6 


300 


137.2 


141. 5 


203.8 


235-5 


55 


23-5 


24.6 


35-0 


41.6 


305 


139-7 


144.0 


207 . 2 


239.5 


60 


25.6 


26.8 


38.4 


45-6 


310 


142 .2 


146.6 


210. 7 


243-3 


65 


27.8 


29.1 


41 .9 


49-5 


315 


144-7 


149- 1 


214. 1 


247.4 


70 


30.0 


31-3 


45-4 


53-5 


320 


147.2 


I5I-7 


217.6 


251-3 


75 


32 .2 


33-6 


48.8 


57-5 


325 


149-7 


154-3 


221.0 


255-3 


80 


34-4 


35-9 


52.3 


61 .4 


330 


152.2 


156.8 


224.4 


2S9-3 


85 


36.7 


38.2 


55-7 


65.4 


335 


154.7 


159-4 


227.9 


263.3 


90 


38.9 


40.4 


59-2 


69 -3 


340 


157.3 


162 .0 


231-3 


267. 1 


95 


41. I 


42. 7 


62.6 


73-3 


345 


159-8 


164.6 


234-7 


271 . 1 


100 


433 


45-0 


66.1 


77-3 


350 


162 . 4 


167. 2 


238.2 


275.0 


105 


45-5 


47-3 


69.5 


81.2 


355 


164.9 


169.8 


241 .6 


279.0 


no 


47-8 


49-6 


73-0 


85.2 


360 


l675 


172.5 


245-1 


282.9 


n5 


50.0 


51-9 


76.4 


89.2 


365 


170. I 


I75-I 


248.5 


286.9 


120 


52.3 


543 


79-8 


93-1 


370 


172.7 


177.7 


252 .0 


290.8 


125 


54-5 


56.6 


833 


97.1 


375 


175-3 


180.4 


255-4 


294.8 


130 


56.8 


58.9 


86.7 


101 .0 


380 


177.9 


183.0 


258.8 


298.7 


135 


59-o 


61.2 


90. 2 


105.0 


38s 


180.5 


185.7 


262.3 


302.7 


140 


61.3 


63.6 


93-6 


109 .0 


390 


183. 1 


188.4 


265.7 


306.6 


145 


63.6 


65-9 


97-1 


112 .9 


395 


185.7 


191 .0 


269. 1 


310.6 


150 


659 


68.3 


100.5 


116. 9 


400 


188.4 


193-7 


272 .6 


3M.5 


155 


68.2 


70.6 


104.0 


120.8 


405 


191 .0 


196.4 


276.0 


3IK.5 


160 


70.4 


73-0 


107.4 


124.8 


410 


193-7 


199- 1 


279-5 


322.4 


165 


72.8 


75-3 


no. 9 


128.8 


415 


196.3 


201.8 


282 .9 


326.3 


170 


75-i 


77-7 


114. 3 


132.7 


420 


199.0 


204.6 


286.3 


330.3 


175 


77-4 


80.1 


117. 7 


136.7 


425 


201 . 7 


207.3 


289.8 


334-2 


180 


79-7 


82.5 


121 . 2 


140.6 


430 


204.4 


210.0 


293-2 


338.3 


185 


82.0 


84.9 


124.6 


144-6 


435 


207. 1 


212.8 


296.6 


342.1 


190 


84.3 


87.2 


128. 1 


148.6 


440 


209 . 8 


215-5 


300. 1 


346.1 


195 


86.7 


89.6 


I3I-5 


152.5 


445 


212.5 


218.3 


3035 


350.0 


200 


89.0 


92 .0 


I35-0 


156. s 


450 


215.2 


221 . 1 


306.9 


353-9 


205 


91.4 


94-5 


138.4 


160. 4 


455 


218.0 


223.9 


310.4 


3579 


210 


93-7 


96.9 


141. 9 


164.4 


460 


220. 7 


226.7 


313.8 


361.8 


215 


96. 1 


99-3 


145-3 


168.3 


465 


223.5 


229.5 


317.3 


365.8 


220 


98.4 


101 .7 


148.7 


172.3 


470 


226. 2 


232.3 


320.7 


369.7 


225 


100. 8 


104. 2 


152 .2 


176.2 


475 


229.0 


235-1 


324.1 


373-7 


230 


103.2 


106.6 


155-6 


180.2 


480 


231.8 


237-9 


327.6 


377-6 


235 


105 .6 


109. 1 


159. 1 


184.2 


485 


234.6 


240.8 


33io 


381. 5 


240 


108.0 


in. 5 


162.5 


188. 1 


490 


237.4 


243-6 


334-4 


385-5 


245 


no. 4 


114. 


166.0 


192 . 1 












250 


112. 8 


116. 4 


169.4 


196.0 












355 


115. 2 


118. 9 


172.8 


200.0 













APPENDIX A. 

Table XIII. 

EXTRACT IN BEER- WORT. 

(According to Schultzand Ostermann.) 



249 



Specific 


Extract. 


Specific 


Extract. 


Specific 


Extract. 


Specific 


Extract. 


Gravity at 


Per cent 


Gravity at 


Per cent. 


Gravity at 


Per cent. 


Gravity at 


Per cent. 


i 5 ° C. 


by Weight. 


>5°C. 


by Weight. 


15° C. 


by Weight. 


.5°C. 


by Weight, 


1 .OOOO 


O.OO 


I 0235 


6.07 


I . 0470 


II.89 


I.0705 


17-59 


1 .0005 


O.13 


I . 0240 


6.I9 


1-0475 


I2.0I 


I .0710 


17.70 


1 .0010 


O.26 


I.O245 


6.31 


I . 0480 


12 . 14 


1-0715 


17.81 


1. 0015 


0-39 


I.0250 


6.44 


I.0485 


12 . 26 


I .0720 


17.93 


1 .0020 


O.52 


^0255 


6.58 


I . 0490 


I2.38 


I.0725 


18.04 


1 .0025 


O.66 


1 .0260 


6.71 


1-0495 


I2.50 


I.0730 


18.15 


I . 0030 


O.79 


1.0265 


6.85 


I .0500 


I2.63 


I 0735 


18.26 


1-0035 


O.92 


1 .0270 


6.99 


1-0505 


12-75 


I .0740 


18.38 


1 . 0040 


I.05 


1.0275 


7.12 


I. 0510 


12.87 


I 0745 


18.49 


1 . 0045 


I. 18 


1 .0280 


7. 26 


1-0515 


12.99 


I.075O 


18.59 


1 .0050 


i-3i 


1.0285 


7-37 


I .0520 


13.12 


I 0755 


18.70 


1-0055 


1.44 


1 .0290 


7.48 


I.0525 


I3.24 


I .0760 


18.81 


1 .0060 


1.56 


1-0395 


7.60 


I 0530 


I3-36 


I.0765 


18.91 


1 . 0065 


1 .69 


1.0300 


7-7i 


1-0535 


I3-48 


I.0770 


19.02 


1 . 0070 


1.82 


I -030 5 


7.82 


I . 0540 


I3.6I 


I0775 


19. 12 


1.0075 


i-95 


1. 0310 


7-93 


I 0545 


13-73 


T .O78O 


I9.23 


1 .0080 


2.07 


1-0315 


8.04 


I-0550 


13-86 


I.O785 


19.33 


1 .0085 


2. 20 


1.0320 


8.16 


IO555 


I3-98 


I .O79O 


19.44 


1 .0090 


2-33 


!032 5 


8.27 


I . 0560 


14. 11 


I-0795 


19-56 


1.0095 


2.46 


1.0330 


8.40 


1-0565 


14.23 


I O8OO 


19.67 


I .0100 


2.58 


I 0335 


8-53 


I.0570 


I4-36 


I.O8O5 ' 


19.79 


1. 0105 


2.71 


1.0340 


8.67 


LO575 


74.49 


I. 08lO 


19.91 


1 .01 10 


2.84 


J0345 


8.80 


I .0580 


14.62 


I. O8I5 


20.03 


1.0115 


2.97 


1-0350 


8-94 


I.0585 


14-75 


I .0820 


20. 14 


1 .0120 


3.10 


1-0355 


9.07 


I . 0590 


14.89 


I.0825 


20.26 


1-0125 


3-23 


1 . 0360 


9. 21 


1-0595 


15.02 


I .O83O 


20.37 


1. 0130 


3-35 


1-0365 


9-34 


I . 0600 


15-14 


LO835 


20.48 


i- OI 35 


3-48 


1.0370 


9-45 


I . 0605 


1525 


I . O84O 


20.59 


1 .0140 


3-6i 


1 0375 


9-57 


I .0610 


1536 


I.O845 


20. 70 


1. 0145 


3-74 


1.0380 


9.69 


I. 0615 


15.47 


I .O85O 


20.8I 


1. 0150 


3-87 


1-0385 


9.81 


I .0620 


I5-58 


I.0855 


20.93 


1-0155 


4.00 


1.0390 


9.92 


I.0625 


1569 


I . O86O 


21 .06 


1 .0160 


4-13 


!0395 


10.04 


I . 0630 


15.80 


I.0865 


21 . 19 


1. 0165 


4.26 


1 . 0400 


10. 16 


IO635 


1592 


I .O87O 


21-33 


1 .0170 


4-39 


1.0405 


10.27 


I . 0640 


16.03 


I.O875 


21-43 


1. 0175 


4-53 


1 .0410 


10.40 


I . 0645 


16. 14 


I.O88O 


21-54 


1 .0180 


4.66 


1-0415 


10.52 


I . 0650 


16.25 


I.O885 


21 .64 


1. 0185 


4-79 


1 . 0420 


10.65 


I 0655 


16.37 


I . O89O 


21-75 


1 .0190 


4-93 


1.0425 


10.77 


I . 0660 


16.50 


IO895 


21.86 


- 1. 0195 


5.06 


1.0430 


10.90 


I . 0665 


16.62 


I . 0900 


21.98 


1 . 0200 


5.20 


J0435 


11.03 


I .0670 


16.74 


I . 0905 


22.08 


1 .0205 


5-33 


1 . 0440 


11. 15 


I.0675 


16.86 


I .O9IO 


22. 19 


1 .0210 


5-45 


1.0445 


11.28 


I . 0680 


16.99 


I-09I5 


22.30 


1. 0215 


5-57 


1 . 0450 


11 .40 


I.0685 


17. 11 


I .0920 


22.41 


1 .0220 


5 70 


1 0455 


1 1 ■ 53 


I . 0690 


17.23 


I . 0925 


22.52 


1 .0225 


5-82 


1 . 0460 


11.65 


1.0695 


17-35 


I . O93O 


22.63 


1 .0230 


5-94 


1.0465 


11.77 


I .0700 


17.48 


I 0935 


22.73 



250 



APPENDIX A. 



Table XIII. — Continued. 

EXTRACT IN BEER-WORT. 
(According to Schultz and Ostermann.) 



Specific 


Extract. 


Specific 


Extract. 


Specific 


Extract. 


Specific 


Extract. 


Gravity at 


Per cent. 


Gravity at 


Per cent 


Gravity at 


Per cent. 


Gravity at 


Per cent. 


. ..5°C. 


by Weight. 


15° C. 


by Weight. 


15° L- 


by Weight 


15° C. 


by Weight. 


I . 0940 


22.84 


I . I020 


24-53 


I . I IOO 


26. 27 


1. 1 180 


27.88 


1-0945 


22.94 


I. 1025 


24.64 


I.IIO5 


26.37 


1.1185 


27.98 


1.0950 


23-05 


I . IO3O 


24-74 


I . II IO 


26.48 


I . 1 1 90 


28.09 


1-0955 


23.16 


I • IO35 


24.85 


I.III5 


26.58 


1. "95 


28.19 


I . 0960 


23.27 


I . IO40 


24.96 


I . 1 1 20 


26.68 


1 . 1 200 


28.28 


I.0965 


23-37 


I . IO45 


25.07 


I.II25 


26.79 


1-1205 


28.38 


I .0970 


23.48 


I . 1050 


25.18 


I. 1 130 


26.89 


1 . 1210 


28.48 


I.0975 


23-59 


I IO55 


25.29 


I.II35 


26.99 


1.1215 


28.58 


I . 0980 


23.69 


I . IO60 


25.40 


I . I I40 


27.09 


1 . 1220 


28.68 


I . 0985 


23.80 


I. IO65 


25-50 


I- 1 145 


27.19 


1. 1225 


28.78 


I . 0990 


23.90 


I . IO70 


25.61 


I.II50 


27.29 


1 . 1230 


28.88 


I.0995 


24.01 


I. IO75 


25-71 


III55 


27.38 


1 1235 


28.98 


I . IOOO 


24. 1 1 


I . IO80 


25.82 


I . I l6o 


27.48 


1 . 1 240 


29.08 


I. 1005 


24.21 


I . IO85 


25-93 


I.H65 


27.58 


1. 1245 


29.18 


I . IOIO 


24.32 


I . IO90 


26.05 


I . 1 1 70 


27.68 


1. 1250 


29. 28 


1.1015 


24-43 


I . IO95 


26. 16 


III75 


27.78 


L1255 


29.38 



APPENDIX A. 
LOGARITHMS OF NUMBERS. 



251 



It « 






















Proportional Parts. 


£j3 





1 


2 


3 ' 


4 


5 





7 


8 


9 






2 £ 






















1 


2 


3 


4 


5 


6 


i 7 


8 


9 


IO 


0000 


0043 


0086 


0128 


0170 


1 I 
0212 0253 0294 


0334 


0374 


4 


S 


1 2 


17 


21 


25!2g 


33 


37 


II 


0414 


0453 


0492 


0531 


0569 


0607 


0645 0682 


0719 


0755 


4 


8 


1 1 


15 


19 


23 


26 


30 


34 


12 


0792 


0828 


0864 


0899 


0934 


0969 


1004 1038 


1072 


1 106 


J 


7 


10 


14 


1 


21 


24 


28 


3i 


13 


"39 


ii73 


1206 


1239 


1271 


1303 


1335 1367 


1399 


1430 


3 


6 


10 


13 


IC 


19 


23 


26 


29 


14 


1461 


1492 


1523 


1553 


1584 


1614 


1644 


( X6 73 


1703 


1732 


3 


6 


9 


1 2 


is 


18 


21 


24 


27 


15 


1761 


1790 


1818 


1847 


1875 


1903 


1931 


1 
,1959 


1987 


2014 


3 


6 


8 


1 1 


14 


17 


20 


22 


25 


16 


2041 


2068 


2095 


2122 


2148 


2175 


2201 


^227 


2253 


2279 


3 


5 


8 


11 


13 


16 


18 


21 


24 


17 


2304 


2330 


2355 


2380 


2405 


2430 


2455 


2480 


2504 


2529 


2 


5 


7 


10 


1 2 


|- IS 


17 


20 


22 


18 


2553 


2577 


2601 


2625 


2648 


2672 


2695 


2718 


2742 


2765 


2 


5 


7 


9 


1 2 


14 


16 


19 


21 


19 


2788 


2810 


2833 


2856 


2878 


2900 


2923 


2945 


2967 


2989 


2 


4 


7 


9 


1 1 


13 


16 


18 


20 


20 


3010 


3032 


3054 


3075 


3096 


3n8 


3i39 


3l60 


3181 


3201 


2 


4 


6 


8 


1 


13 


15 


17 


19 


21 


3222 


3243 


3263 


3284 


3304 


3324 


3345 


33 6 5 


3385 


3404 


2 


4 


6 


8 


10 


12 


14 


16 


18 


22 


3424 


3444 


34 6 4 


3483 


3502 


3522 


354i 


356o 


3579 


3598 


2 


4 


6 


8 


10 


1 2 


14 


15 


17 


23 


3617 


3636 


3655 


3674 


3692 


37" 


3729 


3747 


3766 


3784 


2 


4 


6 


7 


9 


1 1 


13 


IS 


17 


24 ' 


3802 


3820 


3838 


3856 


3874 


3892 


3909 


3927 


3945 


3962 


2 


4 


5 


7 


9 


1 1 


1 2 


14 


16 


25 


3979 


3997 


4014 


4031 '4048 


4065 


4082 


4099 


4116 


4133 


2 


3 


5 


7 


9 


10 


12 


14 


1 5 


26 


4150 


4166 


4183 


4200 4216 


4232 l 4 249 , 4265 


4281 


4298 


2 


3 


5 


7 


8 


10 


11 


13 


15 


27 


4314 


4330 


4346 


4362 4378 


4393 


4409 4425 4440 


4456 


2 


3 


5 





8 


9 


1 1 


13 


14 


28 


4472 


4487 


4502 


4518 4533 


4548 


4564 4579 4594 


4609 


2 


3 


5 


6 


8 


9 


1 1 


12 


14 


29 


4624 


4639 


4654 


4669 4683 


4698 


47134728 


4742 


4757 


I 


3 


4 





7 


9 


10 


12 


13 


30 


477i 


4786 


4800 


4814 


4829 


4843 


4857 


4871 


4886 


4900 




3 


4 


6 


7 


9 


10 


1 1 


13 


31 


+914 


49284942 


4955 4969 


4983 


4997 501 1 


5024 


5038 




3 


4 





7 


8 io 


11 


12 


32 


5051 


50655079 


5092 5105 


5ii9 


51325145 


5i59 


5172 




3 


4 


5 


7 


8 


9 


11 


12 


33 


5i85 


5198 5211 


52245237 


5250 


52635276 


5289 


5302 




3 


4 


5 


6 


8 


9 


10 


12 


34 


5315 


5328.5340 


5353 5366 


5378 


539i 


5403 


54i6 


5428 




3 


4 


5 


6 


8 


9 


10 


11 


35 


544i 


5453^465 


5478 5490 


5502 


55H 


5527 


5539 


555i 




2 


4 


5 


6 


7 


, 


10 


11 


36 


5563 


55755587 


5599 561 1 


5623 


5635 


5647 


5658 


5670 




2 


4 


5 


6 


7 


8 


1 


11 


37 


5682 


5694 57°5 


5717 


5729 


5740 


5752 


5763 


5775 


5786 




2 


3 


5 


6 


» 


8 


9 


10 


38 


5798 


58095821 


5832 


5843 


5855 


5866 


5877 5888 


5899 




2 


3 


5 


6 


7 


8 


9 


10 


39 


59i 1 


5922 


5933 


5944 


5955 


5966 


5977 


5988 5999 


6010 




2 


3 


4 


5 


7 


8 


9 


10 


40 


6021 


6031 


6042 


6053 


6064 


6075 


6085 


6096 


6107 


6117 




2 


3 


4 


5 


6 


8 


9 


IO- 


4i 


6128 


6138 6149 


61606170 


6180 


6191 


6201 


6212 


6222 




2 


3 


4 


5 


6 


7 


8 


9 


42 


6232 


6243^253 


6263 


6274 


6284 


6294 


6304 


63H 


6325 




2 


3 


4 


5 


6 


7 


8 


9 


43 


6335 


6345 


6355 


6365 


6375 


6385 


6395 


6405 


6415 


6425 




2 


3 


4 


5 


6 


7 


8 


9 


44 


6435 


6444 


6454 


6464 


6474 


6484 


6493 


6503 


65X3 


6522 




2 


3 


4 


' 5 


6 


7 


8 


9 


45 


6532 


6542 


6551 


6561 


6571 


6580 


6590 


6599 


6609 


6618 




2 


3 


4 


5 


6 


7 


8 


9 


46 


6628 


6637 


6646 


6656 


6665 


6675 


6684 


6693 6702 


6712 




2 


3 


4 


5 


6 


7 


7 


8 


47 


S721 


6730 


6739 


6749 


6758 


6767 


67761678516794 


6803 




2 


3 


4 


5 


5 


6] 


7 


8 


48 


6812 


6821 


6830 


6839 


6848 


6857 


68666875 6884 


6893 




2 


3 


4 


4 


5 


6 


7 


8 


49 


6902 


691 1 


6920 


6928 


6937 


6946 


6955 


6964 


6972 


6981 




2 


3 


- 


4 


5 


6 


7 


8 


50 


6990 


6998 


7007 


7016 


7024 


7033 


7042 


7050 


7059 


7067 




2 


3 


3 


4 


s 


6 


7 


8 


5i 


7076 


7084 


7093 


7101 


7110 


7118 


7126 


7135 


7143 


7152 




2 


3 


3 


4 


5 


6 1 7 


8 


52 


7160 


7168 


7177 


7185 


7i93 


7202 


7210 


7218 


7226 


7235 




2 


2 


3 


4 


.5 


61 7 


7 


53 


7243 


7251 


7259 


7267 


7275 


7284 


7292 


7300 


73o8 


73I 6 




2 


2 


3 


4 


5 


6 6 


7 


54 


7324 


7332 


7340 


7348 7356 


7364 


7372 


738o l 7388f73 9 6 


I 2 


2 


3 


4 


5 


6 1 


6 


7 



*D* 








APPENDIX A. 
LOGARITHMS OF NUMBERS. 




<a 

*<3 u 




















Proportional Parts. 


Ca 





1 


2 


3 


4 


5 


6 


7 


8 


9 




2 E 




















12 3 4 


5 6 7 8 9 


55 


7404 


7412 


74i9 


7427 


7435 


7442 


745i 


7455 


7466 


» 7474 1223 


4SS67 


56 


7482 


749c 


7497 


7505 


7513 


752C 


7528 


753^ 


7542 


755i 1223 


4 5 5 6 7 


57 


7559 


7566 


7574 


7582 


7589 


7597 


7604 


7612 


7615 


7627 I 2 3 


4 5 67 


58 


7634 


7642 


7649 


7657 


7664 


7672 


7679 


7686 


7694 


77°i 1 1 2 3 


4 4 5 7 


59 


7709 


7716 


7723 


773i 


7738 


7745 


7752 


7760 


7767 


7774 1 1 2 3 


4 4 5 6 7 


60 


7782 


7789 


77967803 


7810 


7818 


7825 


7832 


7839 


7846 1 2 3 


4 4 5 6 6 


61 


7853 


7860 


78687875 


7882 


7889 


7896 


7903 


7910 


7917 112 


4 4 5 6 6 


62 


7924 


793i 


7938i7945 


7952 


7959 


7966 


7973 


7980 


7987 1 1 2 3 


3 4 5 6 6 


63 


7993 


8000 


8007 8014 


8021 


8028 


8035 


8041 


8048 


8055 1 1 2 3 


3 4 5 5 6 


64 


8062 


8069 


80758082 


8089 


8096 


8102 


8109 


8116 


8122 1 1 2 3 


3 4 5 5 6 


65 


8129 


8136 


8i42'8i49 


8156 


8162 


8169 


8176 


8182 


8189 1 1 2 3 


3 4 5 5 6 


66 


8i95 


8202 


8209:8215 


8222 


8228 


8235I8241 


8248 


8254 1 1 2 3 


3 4 5 5 6 


67 


8261 


8267 


8274I8280 


8287 


8293 


8299 


8306 


8312 


8319 1 1 2 3 


3 4 5 5 6 


68 


8325 


8331 


8338|8 3 44 


835i 


83578363 


8370 


8376 


8382 1 1 2 3 


3 4 4 5 6 


69 


8388 


8395 


8401 8407 


8414 


8420 8426 


8432 


8439 


8445 1 1 2 2 


3 4 4 5 6 


70 


8451 


8457 


846318470 


8476 


8482 8488 


8494 


8500 


8506 1 1 2 2 


3 4 4 5 6 


7i 


8513 


8519 


85258531 


8537 


8543'8549 


8555 


8561 


8567 1 1 2 2 


3 4 4 5 5 


72 


8573 


8579 


85858591 


8597 


8603 


8609 


8615 


8621 


8627 1 1 2 2 


3 4 4 5 5 


73 


8633 


8639 


864 5 |86 5 i 


8657 


8663 ! 8669 


8675 


8681 


8686 1 1 2 2 


3 4 4 5 5 


74 


8692 


8698 


8704 


8710 


8716 


87228727 


8733 


8739 


8745 x x 2 2 


3 4 4 5 5 


75 


875i 


8756 


8762 


8768 


8774 


8779 


8785 


8791 


8797 


8802 1 1 2 2 


3 3 4 5 5 


76 


8808 


881488208825 


8831 


8837 


8842 


8848 


8854 


8859 1 1 2 2 


3 3 4 5 5 


77 


8865 


8871 


88768882 


8887 


8893 


8899 


8904 


8910 


8915 1 1 2 2 


3 3 4 4 5 


78 


8921 


8927 


89328938 


8943 


8949 


8954 


8960 


8965 


8971 i 1 2 2 


3 3 4 4 5 


79 


8976 


8982 


89878993 


8998 


9004 


9009 


9015 


9020 


9026 1 1 2 2 


3 3 4 4 5 


80 


9031 


9036 


9042 9047 


9053 


9058 


9063 


9069 


9074 


9079 1 1 2 2 


3 3 4 4 5 


81 


9085 


9090 


9096 9 10 1 


9106 


9112 


9117 


9122 


9128 


9133 x x 2 2 


3 3 4 4 5 


82 


9138 


9143 


9H99I54 


9159 


9165 


9170 


9*75 


9180 


9186 1 1 2 2 


3 3 4 4 5 


83 


9191 


9196 


9201 9206 


9212 


9217 


9222 


9227 


9232 


9238 1 1 2 2 


3 3 4 4 5 


84 


9243 


9248 


9253 


9258 


9263 


9269 


9274 


9279 


9284 


9289 1 1 2 2 


3 3 4 4 5 


85 


9294 


9299 


9304 


93°9 


93 J 5 


9320 


9325 


9330 


9335 


9340 1 1 2 2 


3 3 4 4 5 


86 


9345 


9350 


9355 


9360 


93 6 5 


9370 


9375 


9380 


9385 


9390 1 1 2 2 


3 3 4 4 5 


87 


9395 


9400 


9405 


9410 


9415 


9420 


9425 


9430 


9435 


9440 1 1 2 


2 3 3 4 4 


88 


9445 


9450 


9455 


9460 


9465 


9469 


9474 


9479 


9484 


9489 1 1 2 


2 3 3 4 4 


89 


9494 


9499 


95°4 


9509 


9513 


95i8 


9523 


9528 


9533 


9538 1 1 2 


2 3 3 4 4 


90 


9542 


9547 


9552 


9557 


9562 


9566 


957i 


9576 


958i 


9586 1 1 2 


2 3 3 4 4 


9i 


9590 


9595 


9600 


9605 


9609 


9614 


9619 


9624 


9628 


9633 1 1 2 


2 3 | 3 4 4 


92 


9638 


9643 


9647 


9652 


9657 


9661 


9666 


9671 


9675 


9680 1 1 2 


2 3 3 4 4 


93 


9685 


9689 


9694 


9699 


9703 


9708 


9713 


9717 


9722 


9727 1 1 2 


2 3 3 4 4 


94 


973i 


9736 


974i 


9745 


9750 


9754 


9759 


9763 


9768 


9773 1 1 2 


2 3 3 4 4 


95 


9777 


9782 


9786 


9791 


9795 


9800 


9805 


9809 


9814 


9818 1 1 2 


2 3 3 4 4 


96 


9823 


9827 


9832 


9836 


9841 


9845 


9850 


9 8 54 


9859 


9863 1 1 2 


2 3 3 4 4 


97 


9868 


9872 


9877 


9881 


9886 


9890 


9894 


9899 


9903 


9908 1 1 2 


2 3 3 4 4 


98 


9912 


9917 


9921 


9926 


9930 


9934 


9939 


9943 


9948 


9952 1 1 2 


2 3 3 4 4 


99 


9956 


9961 


9965 9969 


9974 


9978 


998^ 


9987 


999i 


9996 1 1 2 


2 3 3 3 4 















APPENDIX A. 




253 


ANTILOGARITHMS. 






















Proportional Paits. 


ki 





1 


2 


2 


4 


5 


6 


7 


8 


9 




O >- 

t-1 


12 3 4 


5 6 7 8 9 


.OO 


1000 


1002 


1005 


1007 


1009 


1012 


IOli 


1016 


IOIC 


1021 1 1 


x 1 2 2 2 


.01 


1023 


1026 


1028 


1030 


1033 


1035 


io 3 £ 


1040 


1042 


1045 1 1 


1122a 


.02 


1047 


1050 


1052 


io 54 


1057 


1059 


1062 


1064 


1067 


1069 001 1 


1 1 2 2 a 


.03 


1072 


1074 


1076 


1079 


1081 


1084 


1086 


1089 


1091 


1094 1 i 


1 1 2 2 3 


.04 


1096 


1099 


1 102 


1 104 


1 107 


1 109 


III2 


1 1 14 


1117 


1 1 19 1 1 1 


12222 


.05 


1122 


1125 


1127 


1 1 30 


1132 


1135 


1138 


1 140 


1143 II 46 I I I 


12 2 2 2 


.06 


114811151 


1153 


1 1 56 


1159 


1161 


I 164 


1167 


1169 1172 I I I 


12 2 2 2 


.07 


1175J1178 


1 180 


"83 


1186 


1189 


II9I 


1194 


1197 11991 I I I 


12 2 2 2 


.08 


1202 1205 


1208 


1211 


1213 


1216 


1219 


1222 


1225 


1227I0 1 1 1 


12 3 2 3 


.09 


1230 1233 


1236 


1239 


1242 


1245 


1247 


1250 


1253 


1 256J 1 1 1 


12 2 2 3 


.IO 


1259 


1262 


1265 


1268 


1271 


1274 


1276 


1279 


1282 


1285 1 1 1 


12 2 2 3 


.11 


1288 


1291 


1294 


1297 


1300 


i3°3 


I306 


1309 


1312 


1315 1 1 1 


2 2 2 2 3 


.12 


1318 


1321 


1324 


1327 


1330 


1334 


1337 


1340 


1343 


1346 1 1 1 


2 2 2 2 3 


.13 


1349 


1352 


1355 


1358 


1361 


1365 


I368 


1371 


1374 


1377 1 1 1 


2 2 2 3 3 


.14 


1380 


1384 


1387 


1390 


1393 


1396 


I4OO 


i4°3 


1406 


1409 1 1 1 


2 2 2 3 3 


.15 


H J 3 


1416 


1419 


1422 


1426 


1429 


1432 


H35 


1439 


1442 1 1 1 


2 2 2 3 3 


.16 


1445 


1449 


1452 


1455 


1459 


1462 


I466 


1469 


1472 


1476 1 1 1 


22233 


.17 


1479 


1483 


i486 


1489 


1493 


1496 


I5OO 


1503 


1507 


1510 1 1 1 


2 2 2 3 3 


.18 


1514 


1517 


1521 


1524 


1528 


1531 


1535 


1538 


1542 


1545 1 1 1 


2 2 2 3 3 


.19 


1549 


1552 


1556 


1560 


1563 


1567 


I570 


1574 


1578 


1581 o- I I I 


22333 


.20 


1585 


1589 


1592 


1596 


1600 


1603 


1607 


1611 


1614 


1618 1 1 1 


22333 


.21 


1622 


1626 


1629 


1633 


1637 


1641 


1644 


1648 


1652 


1656 1 1 2 


2 2 3 3 3 


.22 


1660 


1663 


1667 


1671 


1675 


1679 


1683 


1687 


1690 


1694 1 1 2 . 


2 2 3 3 3 


.23 


1698 


1702 


1706 


1710 


1714 


1718 


1722 


1726 


173° 


1734 1 1 2 . 


'2334 


•24 


1738 


1742 


1746 


I750 


1754 


1758 


1762 


1766 


1770 


1774 1 1 2 5 


•2334 


.25 


1778 


1782 


1786 


1791 


1795 


1799 


1803 


1807 


1811 


1816 1 1 2 : 


'2334 


.26 


1820 


1824 


1828 


1832 


1837 


1841 


1845 


1849 


1854 


T858 1 1 2 2 


3 3 3 4 


-27 


1862 


1866 


1871 


1875 


1879 


1884 


1888 


1892 


1897 


19OI 1 1 2 2 


3 3 3 4 


.28 


i9°5 


1910 


1914 


1919 


1923 


1928 


1932 


1936 


1 941 


1945 x 1. a s 


3 3 4 4 


.29 


1950 


1954 


1959 


1963 


1968 


1972 


1977 


1982 


1986 


1 99 I 1 1 2 5 


3 3 4 4 


.30 


1995 


2000 


2004 


7009 


2014 


2018 


2023 


2028 


2032 


2037 1 1 2 2 


3 3 4 4 


.31 


2042 


2046 


2051 


2056 


2061 


2065 


2070 


2075 


2080 


2084 1 1 2 1 


3 3 4 4 


-32 


2089 


2094 


2099 


2104 


2109 


2113 


2Il8 


2123 


2128 


2133 1 1 22 


3 3 4 4 


•33 


2138 


2143 


2148 


2153 


2158 


2163 


2l68 


2173 


2178 


2183 1 1 2 2 


3 3 4 4 


• 34 


2188 


2193 


219^ 


2203 


2208 


2213 


2218 


2223 


2228 


2234 1 1 2 2 3 


3 4 1 4 5 


• 35 


2239 


2244 


2249 


2254 


2259 


2265 


2270 


2275 


2280 


2286 1 1 2 2 3 


3 4 4 5 


.36 


2291 


2296 


2301 


2307 


2312 


2317 


2323 


2328 


2333 


2339 1 1 2 2 3 


3 4 4 5 


• 37 


2344 


2350 


2355 


2360 


2366 


2371 


2377 


2382 


2388 


2393 1 1 2 2 ; 


3 4 4 5 


.38 


2399 


2404 


24 1 c 


Hi5 


2421 


2427 


2432 


2438 


2443 


2449 1 1 2 2 ; 


3 4 4 5 


• 39 


2455 


2460 


246C 


2472 


2477 


2483 


2489 


2495 


2500 


2506 1 1 2 2 ; 


3 4 5 5 


.40 


2512 


2518 


2522 


2529 


2535 


2541 


2547 


2553 


2559 


-564 1 1 2 2 ; 


4 4 5 5 


.41 


2570 


2576 


2582 


2588 


2594 


2600 


2606 


2612 


2618 


2624 j ! 2 2 


5 4 4 5 5 


.42 


2630 


2636 


2642 


2649 


2655 


2661 


2667 


2673 


2679 


2685 1 1 2 2 . 


5 4 4 5 <•> 


•43 


2692 


2698 


2704 


2710 


2716 


2723 


2729 


2735 


2742 


2748 1 t 2 3 : 


* ' 4 4 5 *> 


•44 


2754 


2761 


2767 


2773 


2780 


2786 


2793 


2799 


2805 


28l2 J 1 2 3 


5 4 4 5 6 


•45 


2818 


2825 


2831 


2838 


2844 


2851 


2858 


2864 


2871 


2877 a 1 2 3 


3 4 5 5 6 


.46 


2884 


2891 


2897 


2904 


291 1 


2917 


2924 


293 1 


2938 


2944 1 1 2 3 


^4556 


•47 


2951 


2958 


2965 


2972 


2979 


2985 


2992 


2999 


3006 


30I3 1 1 2 3 


3 4 5 5 6 


.48 


3020 


3027 


3034 


3041 


3048 


3055 


3062 


3069 


3076 


3083 1 1 2 3 


4 4 5 6 6 


•49 


3090 


3097 


3105 


3112 


1119 


3126 


3133 


3141 


3148131.^ 1 1 2UI 


4 4 5 6 6 



254 












APPENDIX A. 




I 


ANTILOGARITHMS. 


s 




















Proportional Parts. 


rt-5 





1 


2 


3 


4 


5 


6 


7 


8 


9 




o u 


12 3 4 


5 6 7 8 9 


•50 


3162 


3!7o 


3i77 


3184 


3192 


3199 


3206 


3214 


3221 


3228 1 1 2 3 


44567 


.51 


3236 


3243 


3251 


3258 


3266 


3273 


3281 


3289 


3296 


3304 1223 


45567 


•52 


33" 


3319 


3327 


33.34 


3342 


335° 


3357 


3365 


3373 


3381 1223 


45567 


•53 


3388 


3396 


3404 


34 ! 2 


3420 


3428 


3436 


3443 


345i 


3459 1223 


45667 


•54 


3467 


3475 


3483 


3491 


3499 


35o8 


35i6 


3524 


3532 


3540 1223 


45667 


•55 


3548 


3556 


3565 


3573 


358i 


3589 


3597 


3606 


3614 


3622 1223 


45677 


.56 


363 1 


3639 


3648 


36-56 


3664 


3673 


3681 


3690 


3698 


3707 1233 


45678 


•57 


3715 


3724 


3733 


374i 


3750 


3758 


3767 


3776 


3784 


3793 1233 


45678 


.58 


3802 381 1 


3819 


3828 


3837 


3846 


3855 


3864 


3873 


3882 1234 


45678 


•59 


3890 


3899 


39o8 


39*7 


3926 


3936 


3945 


3954 


3963 


3972 1234 


55678 


.6O 


398i 


399o 


3999 


4009 


4018 


4027 


4036 


4046 


4055 


4064 1 2 3 4 


56678 


.61 


4074 4083 


4093 


4102 


4111 


4121 


4130 


4140 


4150 


4159 1234 


5 6 7 8 .9 


.62 


416914178 


4188 


4198 


4207 


4217 


4227 


4236 


4246 


4256 1234 


5 6 7 8 .9 


.63 


4266I4276 


4285 


4295 


4305 


43 1 5 


4325 


4335 


4345 


4355 1 2 3 4 


56789 


.64 


4365I4375 


4385 


4395 


4406 


4416 


4426 


4436 


4446 


4457 1234 


5 6 7 8 .9 


.65 


4467 


4477 


4487 


449.8 


4508 


4519 


4529 


4539 


4550 


4560 1234 


56789 


.66 


457i 


458i 


4592 


4603 


4613 


4624 


4634 


4645 


4656 


4667 1234 


5 6 7 9 10 


.67 


4 6 77 


4688 


4699 


4710 


472i 


4732 


4742 


4753 


4764 


4775 1 2 3 4 


5 7 8 9 10 


.68 


4786 


4797 


4808 


4819 


4831 


4842 


4853 


4864 


4875 


4887 1234 


6 7 8 9 10 


.69 


4898 


49P9 


4920 


4932 


4943 


4955 


4966 


4977 


4989 


5000 1235 


6 7 8 9 10 


•70 


5012 


5Q23 


5035 


5047 


5058 


5070 5082 


50935105 


5117 1245 


6 7 8 9 11 


.71 


5129 


5HO 


5152 


5 l6 4 


5176 


5188I5200 


5212 


5224 


5236 1245 


6 7 8 10 11 


.72 


5248 


5260 


5272 


5284 


5297 


53°9l532i 


5333 


5346 


5358 1245 


6 7 9 10 n 


• 73 


5370 


5383 


5395 


5408 


5420 


5433 


5445 


5458 


5470 


5483 1345 


6 8 9 10 11 


• 74 


5495 


5508 


552i 


5534 


5546 


5559 


5572 


5585 


5598 


561O 1 3 4 5 


6 8 9 10 12 


• 75 


5623 


5636 


5649 


5662 


5675 


5689 


5702 


5715 


5728 


574I 13 4 5 


7 8 9 10 12 


.76 


5754 


5768 


578i 


5794 


5808 


5821 


5834 


5848 


5861 


5875 1 3 4 S 


7 8 9 11 12 


• 77 


5888 


5902 


59 l6 


59 2 9 


5943 


5957 


5970 


5984 


5998 


60I2 13 4 5 


7 8 10 11 12 


.78 


6026 


6039 


6053 


6067 


6081 


6095 


6109 


6124 


6138 


6152 1346 


7 8 10 11 13 


• 79 


6166 


6180 


6194 


6209 


6223 


6237 


6252 


6266 


6281 


6295 13 4 6 


7 9 10 11 13 


.80 


6310 


6324 


6339 


635'3 


6368 


6383 


6397 


6412 


6427 


6442 1346 


7 9 10 12 13 


.81 


6457 


6471 


6486 


6501 


6516 


6531 


6546 


6561 


6577 


6592 2356 


81 9 11 12 14 


.82 


6607 


6622 


6637 


6653 


6668 


6683 


6699 


6714 


6730 


6745 2356 


8 9 11 12 14 


.83 


6761 


6776 


6792 


6808 


6823 


6839 


6855 


6871 


6887 


6902 2356 


8} 9 11 13 14 


.84 


6918 


6934 


6950 


6966 


6982 


6998 


7015 


703 1 


7047 


7063 2356 


8 10 11 13 15 


.85 


7079 


7096 


7112 


7129 


7145 


7161 


7178 


7194 


7211 


7228 2 3 5 7 


8 10 12 13 15 


.86 


7244 


7261 


7278 


7295 


73"" 


7328 


7345 


7362 


7379 


7396 2 3 5 7 


8 10 12 13 15 


.87 


7413 


743° 


7447 


7464 


7482 


7499 


75 l6 


7534 


755i 


7568 235 7 


9 10 12 14 16 


.88 


7586 


7603 


7621 


7638 


7656 


7674 


7691 


7709 


7727 


7745 2457 


911 12 14 16 


.89 


7762 


7780 


7798 


7816 


7834 


7852 


7870 


7889 


7907 


7925 2457 


911 13 14 16 


.90 


7943 


7962 


7980 


7998 


8017 


8035 


8054 


8072 


8091 


8110 2467 


9 11 13 15 17 


.91 


8128 


8i47 


8166 


8185 


8204 


S222 


8241 


8260 


8279 


8299 2468 


9 11 13 i5 17 


.92 


8318 


8337 


8356 


8375 


8395 


8414 


8433 


8453 


8472 


8492 2468 


10 12 14 15 17 


•93 


85 1 1 


853^ 


855i 


8570 


8590 


8610 


8630 


8650 


8670 


8690 2468 


1012141618 


•94 


8710 


8730 


8750 


8770 


8790 


8810 


8831 


8851 


8872 


8892 2468 


10 12 14 16 18 


95 


8913 


8933 


8954 


8974 


8995 


9016 


9036 


9°57 


9078 


9099 2468 


10 12 15 17 19 


.96 


9120 


91:41 


9162 


9183 


9204 


9226 


9247 


9268 


9290 


9311 2468 


11 13 15 17 19 


•97 


9333 


9354 


9376 


9397 


9419 


9441 


9462 


9484 


9506 


9528 2479 


11 13 15 17 20 


.98 


9550 


9572 


9594 


9616 


96^8 


9661 


9683 


9705 


9727 


9750 2' 47 O 


11 13 16 18 20 


•99 19772 


9795 


9817 


9840 986^ 


98869908 9931 


99549977 Ws 1 


11 14 16 18 20 



APPENDIX B. 

REAGENTS. 

AIR ANALYSIS. 

Barium Hydroxide. — A solution containing about 4 grams 
of BaO and 0.2 gram of BaCl 2 to the liter. (1 c.c. = 1 mg. 
C0 2 , approximately.) 

Sulphuric Acid. — Dilute 45.45 c.c. of normal sulphuric 
acid to one liter. ( 1 c.c. = 1 mg. C0 2 .) To standardize the 
solution measure 25 c.c. into a weighed platinum dish, add 
dilute ammonia- water in slight excess,, eyanorate to dryness 
on the water-bath, and dry at 120 C. to constant weight. 

Standard Lime-water. — (For Popular Tests.)— Shake one 
part of freshly slaked lime with 20 parts of distilled water for 
twenty minutes and let the solution stand overnight or until 
perfectly clear. This solution should be very nearly equiva- 
lent to the above standard sulphuric acid. To a liter of dis- 
tilled water add 5 c.c. of a solution of 0.7 gram of phenol- 
phthalein in 100 c.c. of 50 per cent, alcohol and add lime- 
water drop by drop until a slight permanent pink color is 
produced. Add 12.6 c.c. of the above calcium hydroxide 
solution. The resulting solution is the standard lime-water 
used for the tests. 

WATER ANALYSIS. 

For Ammonia. — Water Free from Ammonia. — The am- 
monia-free water used in this laboratory is made by redis- 
tilling distilled water from a solution of alkaline permangan- 

255 



256 



APPENDIX B. 



ate in a steam-heated copper still. The apparatus used is 
shown in Fig. 15. Only the middle portion of the distillate 
is collected. Oftentimes the distillate from a good spring- 
water may be used. 

Nesslers Reagent. — Dissolve 61.750 grams KI in 250 c.c. 
distilled water and add a cold solution of HgCl 2 which has 
been saturated by boiling an excess of the salt and allowing 
it to crystallize out. Add the HgCl 2 cautiously until a slight 
permanent red precipitate (Hgl 2 ) appears. Dissolve this 




Fig. 15. — Still for Ammonia-free Water. 



slight precipitate by adding 0.750 gram powdered KI. Then 
add 150 grams of KOH dissolved in 250 c.c. of water. Make 
up to the liter and allow it to stand overnight to settle. This 
solution should give the required color with ammonia within 
five minutes, and should not precipitate within two hours. 

Alkaline Permanganate. — Dissolve 233 grams of the best 
stick potash in 350 c.c. of distilled water. Filter this strong 



APPENDIX B. 257 

solution, if necessary, through a layer of glass wool on a por- 
celain filter-plate. Dilute with 700 to 750 c.c. of distilled 
water to a sp. gr. of 1.125, add 8 grams of potassium per- 
manganate crystals, and boil down to one liter to free the 
solution from nitrogen. Each new lot of reagent must be 
tested before being used, but when the chemicals used are all 
good there should be no correction needed for ammonia in 
the solution. 

Standard Ammonia Solution. — Dissolve 3.8215 grams . 
chemically pure NH 4 C1 in a liter of water free from ammo- 
nia. This is the strong solution from which the s.andard 
solution is made by diluting 10 c.c. to a liter wkh wa'.er free 
from ammonia. One c.c. of the standard solution = o.orcoi 
gram nitrogen. This solution, like the nitrite standard and 
other dilute solutions, must be preserved in sterilized bottles 
protected from dust and organic matter. 

For Nitrites. — Standard Nitrite Solution. — The pure sil- 
ver nitrite used in making this solution is prepared by the 
double decomposition of silver nitrate and potassium nitrite, 
and repeated crystallizations from water of the rather diffi- 
cultly soluble silver nitrite. 1.1 grams of this silver nitrite 
are dissolved in nitrite-free water, the silver completely pre- 
cipitated by the addition of the standard salt solution used in 
the determination of chlorine, and the solution made up to 
1 liter. 100 c.c. of this strong solution are diluted to 1 liter, 
and 10 c.c. of this last solution again diluted to 1 liter. The- 
rmal solution is the one used in preparing standards. 1 c.c 
= 0.000000 1 gram nitrogen. 

Sulpkanilic Acid. — Dissolve 3.3 grams sulphanilic acid 
in 750 c.c. of water by the aid of heat, and add 250 c.c. 
glacial acetic acid. 

Naphtylamine Acetate. — Boil 0.5 gram of a-naphtylamine 
in 100 c.c. of w ater in a small Erlenmeyer flask for about five. 



258 APPENDIX B, 

minutes, filter through a plug of washed absorbent cotton, 
add 250 c.c. glacial acetic acid, and dilute to a liter. 

For Nitrates. — Standard Nitrate Solution. — Dissolve 
0.720 gram of pure recrystallized KN0 3 in 1 liter of water. 
Evaporate 10 c.c. of this strong solution cautiously on the 
water-bath, moisten quickly and thoroughly with 2 c.c. of 
phenol-disulphonic acid, and dilute to 1 liter for the stand- 
ard solution. 1 c.c. =0.000001 gram nitrogen. 

Phenol-disulphonic Acid. — Heat together- 3 grams syn- 
thetic phenol with 37 grams pure, concentrated H 2 S0 4 in a 
boiling -water bath for six hours. 

For Kjeldahl Process. — Sulphuric Acid. — Sp. gr. 1,84.. 
This should be free from nitrogen. May be obtained from 
Baker and Adamson, Easton, Pa. 

Potassium Hydroxide. — Dissolve 350 grams of the best 
stick potash in ..25 liters of water and boil down to some : 
thing less thai a liter with 3 grams of permanganate crys- 
tals. When cold, dilute to a liter with water free from am-, 
monia. 

For Phosphates. — Ammonium Molybdate. — Dissolve 50 
grams of the pure neutral salt in a liter of distilled water. 

Nitric Acid (sp. gr. 1.07).— One part of acid (sp. gr. 1.42) 
to five parts of water. 

Standard Phosphate Solution. — Dissolve 0.5324 gram of 
pure crystallized sodium phosphate (Na 2 HP0 4 .i2H 2 0) in 
freshly distilled water, add 100 c.c. of nitric acid (1.07), and 
dilute to 1 liter. 1 c.c. =0.0001 gram P 2 5 . The solution 
keeps without change for several months if preserved in 
well-stoppered bottles of hard glass ; after a longer time it 
becomes slightly stronger, owing to the silica dissolved from 
the glass. 

For Chlorine. — Salt Solution. — Dissolve 16.48 grams of 
fused NaCl in a liter of distilled water. For the standard 



APPENDIX B. 259 

solution dilute 100 c.c. of this strong solution to 1 liter. 
1 c.c. =0.001 gram chlorine. 

Silver Nitrate. — Dissolve about 2.42 grams of AgNO s (dry 
crystals) in 1 liter of chlorine-free water. 1 c.c. = .0005 gram 
CI, approximately. Standardize against the NaCl solution. 

Potassium Chromate. — Dissolve 50 grams neutral K 2 CrO i 
in a little distilled water. Add enough AgN0 3 to produce a 
slight red precipitate. Filter and make the filtrate up to a 
liter with water free from chlorine. 

Milk of Alumina for P)e color ization. — Dissolve 125 grams 
of potash or ammonia alum in a liter of distilled water. Pre- 
cipitate the Al(OH) 3 by the cautious addition of NH 4 OH. 
Wash the precipitate in a large jar by decantation until free 
from chlorine, nitrites, and ammonia. 

For Hardness. — Standard Calcium Chloride Solution. — 
Dissolve 0.200 gram of pure Iceland spar in dilute HC1, tak- 
ing care to avoid loss by spattering, and evaporate to dryness 
several times, to remove the excess of acid. Dissolve the 
calcium chloride thus formed in 1 liter of water. 

Standard Soap Solution. — Dissolve 100 grams of the best 
white, dry castile soap In a liter of 80 per cent, alcohol. Of 
this strong solution dissolve 75-100 c.c. in a liter of 70 per 
cent, alcohol. This solution must have 70 per cent, alcohol 
added to it until 14.25 c.c. of it give the required lather with 
50 c.c. of the above CaCl 2 solution. 

Erythrosine Indicator. — Dissolve 0.1 gram of erythrosine 
in 1 liter of water. 

For Iron. — Standard Iron Solution. — Dissolve 0.86 gram 
of ferric ammonium alum, (NH 4 ) 2 S0 4 .Fe 2 (S0 4 ) 3 .24H 2 0, or 
a corresponding amount of the potassium salt in 500 c.c. of 
water, add 5 c.c. HNO s (1.20), and dilute to 1 liter. 1 c:c. = 
0.000 1 gram Fe. 

Potassium Sulphocyanide. — 5 grams per liter. 



26o APPENDIX B. 

Hydrochloric Acid. — i part HC1 (sp. gr. 1.20) to 1 part of 
water. 

Potassium Permanganate. — 5 grams KMn0 4 in 1 liter of 
water. 

For Dissolved Oxygen. — (a) 48 grams of MnS0 4 .4H 2 in 
100 ex. of water; (b) 360 gra^s of NaOH and 100 grams of 
KI in 1 liter of water; (c) HC1, sp. gr. 1.20 

Sodium Thios^lphate Solution. — Dissolve 2$ grams of pure 
recrystallized sodium thiosulphate in 1 liter of water. Dilute 
200 c.c. to 1 liter and standardize against a known K 2 Cr 2 7 
solution. 

For Lead. — Standard Lead Solution. — To a strong solu- 
tion of lead acetate add a slight excess of H 2 S0 4 , filter off 
and wash the precipitate. Dissolve it in ammonium acetate 
solution, made by neutralizing glacial acetic acid with strong: 
ammonia. Make up to a known volume and determine the lead 
in an aliquot part by precipitating with K 2 Cr 2 7 and weigh- 
ing the lead chromate. Dilute an aliquot part to make a con- 
venient standard, say about 1 c.c. = 0.001 gram of Pb. 

FOOD ANALYSIS. 

Acid Mercuric Nitrate. — Dissolve mercury in double its 
weight of nitric acid (sp. gr. 1.42) and dilute the solution 
with five times its volume of water. 

Pumice. — Bits of ignited pumice, about the size of a pea, 
dropped while hot into water and bottled for use. 

Alcohol (for Reichert-Meissl method). — 95 per cent, alcohol 
redistilled from potassium hydroxide. 

Potassium Hydroxide (for Reichert-Meissl method). — One 
part good quality caustic potash dissolved in one part of 
water. 

Iodine Solution (for Hanus' method). — This is conven- 
iently made up according to the directions of Hunt.* Dis- 

* /. Soc. Chem. Ind., 21 (1902), 454. 



APPENDIX B. 26 1 

solve 13.2 grams iodine in 1 liter of glacial acetic acid (99 per 
cent., showing no reduction with bichromate and sulphuric 
acid). This will best be done by adding the acetic acid in 
portions and heating on the water-bath with frequent shaking. 
To the cold solution add enough bromine to double the halogen 
content, as shown by titration. Three c.c. of bromine is suffi- 
cient. A slight excess of iodine is not detrimental. 

Potassium Iodide. — Dissolve 200 grams of potassium iodide 
in 1 liter of water. 

Anhydrous Ether. — Wash ordinary ether several times with 
distilled water and add solid caustic potash until most of the 
water has been removed. Then add small pieces of clean 
metallic sodium until there is no further evolution of hydrogen 
gas. The ether thus prepared should be kept over metallic 
sodium and a tube of calcium chloride should be inserted in 
the stopper, in order to allow of the escape of any accumulated gas. 

Potassium Sulphide. — Dissolve 40 grams of the crystallized 
salt in 1 liter of water and filter through glass wool. 

Potassium Hydroxide (for Kjeldahl process). — Dissolve 700 
grams of the best quality of stick potash in water and dilute 
to 1 liter. 

Basic Lead Acetate. — Boil for half an hour 440 grams of 
lead acetate and 264 grams of litharge in 1500 c.c. of water. 
Cool and dilute to 2 liters. Allow to settle and siphon off 
the clear liquid. (Sp. gr. about 1.27, containing about 35 
per cent, of the basic salt.) 

Ferric Alum. — Dissolve 2 grams of ferric alum in 100 c.c. 
of water, boil the solution until a precipitate appears, and filter. 

Fehling's Solution. — (a) Dissolve 69.28 grams of C.P. crys- 
tallized copper sulphate, carefully dried between blotting-paper, 
in water and make up to 1 liter, including 1 c.c. of strong sul- 
phuric acid; (b) Dissolve 346 grams of sodium potassium tar- 
trate and 100 grams of sodium hydroxide in water and make 
up to a liter. 



BIBLIOGRAPHY. 



The following list comprises some of the more important 
works bearing on the subjects treated in the preceding 
pages. A bibliography of the chemistry of foods com- 
plete to 1882 may be found in the Second Annual Report 
of the New York State Board of Health, and more or less 
complete bibliographies are to be found in Sadtler's ''In- 
dustrial Organic Chemistry," Blyth's " Composition and 
Analysis of Foods," and Leach's " Food Inspection and 
Analysis." 

AIR. 

Air and Rain. R. Angus Smith. Longmans, Green & Co. London. 1872. 

Air and its Relations to Life. Walter N. Hartley. D. Appleton & Co. 
New York. 1875. 

Report on the Air of Glasgow. E. M. Dixon. Robert Anderson. Glas- 
gow. 1877. 

Recherches sur l'Air Confine. A. Braud. Bailliere et Fils. Paris. 1880. 

Air Analysis. J. A. Wanklyn and W. J. Cooper. Kegan Paul, Trench,. 
Trubner & Co. London. 1890. 

Les Poisons de l'Air. N. Grehaut. Bailliere et Fils. Paris. 1890. 

Treatise on Hygiene and Public Health. Vol. I. Thomas Stevenson and 
S. F. Murphy. Blakiston, Son & Co. Phila. 1892. 

Air and Water. Vivian B. Lewes. Methuen & Co. London. 1892. 

Methods for the Determination of Organic Matter in Air. D. H. Bergey. 
Smithsonian Institution. Washington, D. C. 1896. 

The Detection and Measurement of Inflammable Gas and Vapor in the 
Air. Frank Clowes. Crosby, Lockwood & Son. London. 1896. 

Sanitation in Daily Life. Ellen H. Richards. Whitcomb & Barrows. 

Air Currents and the Laws of Ventilation. W. W. Shaw. Cambridge, at 
the University Press. 

VENTILATION, 

Heating and Ventilation of the New Building, Mass. Inst. Tech. S. H. 
Woodbridge. Tech. Quart., 2, 76. 1888. 

263 



264 BIBLIOGRAPHY. 

Heating and Ventilation. J. S. Billings. Sanitary Engineer. New York. 

1893. 
Heating and Ventilating Buildings. Rolla C. Carpenter. John Wiley & 

Sons. New York. 1895. 

WATER. 

Report of the Royal Commission on Water Supply. Great Britain Par- 
liamentary Documents. London. 1869-70. 

Sixth Report of Rivers Pollution Commission, Great Britain. London. 
1876. 

Water Softening and Scientific Filtration. Walter George Atkins. E. & 
F. N. Spon. London. 1880. 

National Board of Health Report for 1882. 

Water Supply (Considered mainly from a Chemical and Sanitary Standpoint). 
W. R. Nichols. John Wiley & Sons. New York. 1883. 

Water Analysis for Sanitary Purposes. E. Frankland. John Van Voorst. 
London. 1890. 

"The Organic Analysis of Potable Waters. J. A. Blair. 1890. 

Drinking Water and Ice Supplies. T. Mitchell Prudden. G. P. Putnam 
& Sons. New York. 1891. 

Potable Water. Floyd Davis. Silver, Burdett & Co. New York. 1891. 

The Action of Water on Lead. John Henry Garrett. H. K. Lewis. 
London. 1891. 

Treatise on Hygiene and Public Health. Vol. I. Thomas Stevenson and 
S. F. Murphy. Blakiston, Son & Co. Phila. 1892. 

Sewage Disposal in the United States. Geo. W. Rafter and M. N. Baker. 
D. Van Nostrand Co. New York. 1894. 

Xes Eaux-d' Alimentation, Epuration, Filtration, Sterilization. Edm. 
Guinochet. Bailliere et Fils. Paris. 1894. 

Micro-Organisms in Water. Percy F. Frankland and Mrs. Percy F. Frank- 
land. London. 1894. 

The Filtration of Public Water Supplies. Allen Hazen. John Wiley & 
Sons. New York. 1895. 

Examination of Water for Sanitary and Technical Purposes. Henry Leff- 
man. Blakiston, Son & Co. Phila. 1895. 

Sewage Disposal on the Farm and Protection of Drinking Water. Theo- 
bald Smith. U. S. Dept. Agr., Farmers' Bull. 43. 1896. 

Water Supply (Considered Principally from a Sanitary Standpoint). W 
P. Mason. John Wiley & Sons. New York. 1903. 

Water Analysis. J. A. Wanklyn and E. T. Chapman. Tenth Ed. Kegan 
Paul, Trench, Triibner & Co. London. 1896. 

Examination of Water and Water Supplies. John C. Thresh. H. A. 
Churchill & Co. London. 1896. 

Mikroskopische Wasseranalyse. Carl Mez. J. Springer. Berlin. 1898. 

A Simple Method of Water Analysis. John C. Thresh. J. & A. Churchill. 
London. 1898. 



BIBLIOGRAPHY. 265 

Water Purification at Louisville, Ky. Geo. W. Fuller. D. Van Nostrand 

Co. New York. 1898. 
Report on Water Purification at Cincinnati, O. Geo. W. Fuller. Board 

of Trustees, Cincinnati. 1899. 
Report of Filtration Commission, Pittsburgh, Pa. 1899. 
Examination of Water (Chemical and Bacteriological). William P. Mason. 

John Wiley & Sons. New York. 1899. 
The Microscopy of Drinking Water. Geo. C. Whipple. John Wiley & 

Sons. New York. 1 899. 
Geological Survey. State of Washington. 1901. 
Report of Streams Examination, Sanitary District of Chicago. 1902. 
Chemical Survey of the Waters of Illinois. 1 897-1902. 
Water and its Purification. S. Rideal. Crosby, Lockwood & Son. London. 

1902. 
Report on Water Purification Investigations. New Orleans Sewerage and 

Water Board. 1903. 
Elements of Water Bacteriology. S. C. Prescott and C.-E. A. Winslow. 

John Wiley & Sons. New York. 1904. 
State Board of Health Reports for Massachusetts, Michigan, Illinois, Ohio. 

The Mass. Reports for 1872-75 and 1890-1900, especially, contain 

many valuable papers, the following being some of the most important 

of them : 
Chemical Examination of Water and Interpretation of Analyses. Thomas 

M. Drown. Rep. Mass State Board of Health, 1892, 319. 
Discussion of Special Topics Relating to the Quality of Public Water Sup- 
plies. F. P. Stearns and T. M. Drown. Rep. Mass. State Board of 

Health, 1890, 717. 
On the Amount of Dissolved Oxygen contained in Waters of Ponds and 

Reservoirs at Different Depths. Thomas M. Drown. Rep. Mass. 

State Board of Health, 1891, 373. 
On the Amount of Dissolved Oxygen contained in Waters of Ponds and 

Reservoirs at Different Depths in Winter under the Ice. Thomas M. 

Drown. Rep. Mass. State Board of Health, 1892, 333. 
On the Mineral Contents of Some Natural Waters in Mass. Thomas M. 

Drown. Rep. Mass. State Board of Health, 1892, 345. 
The Effect of the Aeration of Natural Waters. Thomas M. Drown. Rep. 

Mass. State Board of Health, 1891, 385. 

In addition to the above the following papers contain 
much information of value on special topics relating to 
water supply and water analysis: 

Chemical Examination of Drinking Water. Thomas M. Drown. Proc. 
Soc. Arts., M. I. T., 1887-8, 87. 



266 BIBLIOGRAPHY*. 

THe^ Analysis of Water — Chemical, Microscopical, and -Bacteriological 

Thomas M. Drown. J. N. E. Water Works Assoc, 4 (1889) ,79. 
Uti the Boss on Ignition in Water Analysis. Thomas M. Drown. Tech. 

Quart., 2 (1888), 132. 
The Odor and Color of :] Surface Waters. Thomas M. Drown. Tech. 

Quart., 1 (1888), 256;^ -■ 
Reduction of Nitrates by Bacteria. Ellen H. Richards and George W. 
: V Rolfe! Tech. Quart:; 9 (1 896) , 40. 
The Purification of Water by Freezing. Thomas M. Drown. J. N. E. 

Water Works Assoc, 8 (1893), 46. 
The Filtration of Natural Waters. Thomas M. Drown. J. of the Assoc. 

of Eng. Soc, 9 (1890), 356. - 

A Study of Self-Purification in the Sudbury River. A. G. Woodman, 

C.-E. A. Winslow, and P. Hansen. Tech. Quart., 15, 1902. 
Normal Distribution of Chlorine in Connecticut. H. E. Smith and F. 'SI 

Hollis. Rept. Conn. State B'd Health, 1902. ' 
Water Supplies of S. E. Alaska and the Black Hills of S. Dak; E. H. 

Richards. Tech. Quart., 16,-1903. 
Notes on the Potable Waters of Mexico. E. H. Richards". Trans. Ami 
J Inst. Min. Eng., 1901. ; ; ' ' 

-Rainfall on the Pacific Coast and the Factors of Water Stlpply in California. 

J. Assoc. Eng. Soc, 1903. 



, j WATER. 

Department of Interior. U. S. Geological Survey. Underground Water f Water 

1 Supply and Irrigation Paper. No. 160. Myron L.' Fuller. ' 

Field Assay of Water. No. 151. Marshall O. Leigntoh. 

Value of Pure Water. George C. Whipple. Published by John Wiley- & Sons. 

■ l: New York. ' ' ■ '" ' " ; ' " iv »- : :; " : ''-■ M" «0 

Report of the Commission on Additional Water Supply for the City of New York. 
Appendix VI. ! 

Report of the Committee on Standard Methods of Water Analysis td the Labora- 
tory Section of the American Public ' Health Association. (Reprinted from 
the journal of Infectious Diseases, Supplement No. i.- May, 1965:) 

Disposal of Dairy and Farm Sewage and Water Supply. Oscar Erf. 'Kansas 
State Agricultural College Experiment Station Bulletin. 






BIBLIOGRAPHY. 267 

•'-^ -■■ '-."- ; ■- ;; -m -- FOOD.- •; l'. ; .-!m.-,;m,-! •,;; K-;-: ;-. •.-; 

The list given here is limited to, , books published since 
1890. •/•-* 

Traite General d' Analyse des Beurres. A. J. Zune. H. Lamartin. 

r; : ? ; Paris. 1892. «.* 

Die Menschlichen Nahrungs- u. Genussmittel. J. Konig. Julius Springer. 

j Berlin.- 1893. 

Foods and Dietaries. R. W. Burnet, M.D. . P. Blakiston, Son & Co. 
.,];,, lEhila; £893,, , . . -., , l: ri ■ . f ... : . : . p . : ...-' : 

Analyse des Matieres Alimentaires et Recherche de Leur- Falsifications. 
V/ . ;;/ jCh. r Girar4 et A r ,Dupre. Vve. Ch. Dunod &;P... Vicq. ; : Paris. , .... 1 894. . 
Animal and Vegetable Oils, Fats, Butters and Waxes. C. R. Alder Wright. 

; Jf •Griffin-& Co;- \ London. 1894. . rv ■ •...;: '.,.:... 

Chemistry of Wheat, Flour, and Bread. Wm. Jago. Simpkin Marshall. 
,/j . I.ondon. ; . ^895, ■ ( - <j ., . ■• ■■■ j. .. : . ... .j^j^.a -jfotfj \ . 
The Food Products of the World. Dr. Mary E. Green. Th^ Hotel. World? 

Chicago. 1895. 
The Story of Germ Life. H. W. Conn. Appleton & Co. New York 

-,.. I ?97 T . j, ^ f if ;.,: fV: , ,. V • ; .: ; . t .= . ,? .„....,. ;, , . 

The Relation of Food to Health. George H. Townshe'nd. Witt Publish- 

20 l jngCo. :; St. Louis. 11897;' ' ■•'■ < : : : ' v .•••-;•;•■.■::;,, A =. .;;•■ - : 

The Analysis of Food and Drugs., Part I: ; Mjlk and. Milk, .Products. ., T. 

H. Pearmain and C. G. Moor. Bailliere Tindall & Cox. London.' 

l8 97- ,^ -,v. , u , ... ■,..,......, ,, ,, ; ; ,.,.,-,^ 

Principles and Practice of Agricultural Analysis. Harvey W. Wiley. Chem. 

Pub. Co. Easton, Pa. 1897. ■ if, ' ';< : ■■.:)■■ ■■■. ■•-. ■■.-■. ■ ; , ; ,f 

Testing Milk and its Predicts. E. H. Farririgton and F= W. Woll. Men- 

dota Book Co. Madison, Wis. ■ 1898;- -.L mD - ■'.•: :'■ i .= *j v ■iihniriVj . , 
Chemical Analysis of Oils, Fats, and rWaxes. . Ji . ^ewkowitsch. .--Mac*. 
> ! - ; millMi &<Co. nLdndor/, kgc^uL-iKoqt. •:.-.) !■:•:<■:: .;.?>;{ .;,:.. 
Commercial Organic Analysis. A. H. Allen. Third Ed. Rev.-- by H. Leff- 

man. Blakiston, Son" >&i Co. Phila. ^1^98;: '*■■ ■■■'■- ■■.:■/;:•■-■ 
Die Untersuchung ' ■ landwirtschaftlich und ge'werbiich wichtiger Stoffe. 

J. Konig. Paul Parey; Berlin.- i.i 1898U-: I ■ ■-''■ 
Food Materials ahd^their Adulterations. 1 Ellfeni H,' Richards: Borne 

Science Pub. Co; Boston. (i908; : •-. = >ttv-? ^■■^ -.- 

Plain Words about Food; -The .Rumford Kitchen .Leaflets. Ellen H 

Richards,: Ed. Home Science Pub. Co. Boston. 1899. 
Muscle, Brain, and Diet: A Plea for Simpler Foods. E. 1 H. Miles. Sonnen- 

schien. London.' ^1900. :■ '' V - ■■^vzcqf-r/. ri 

AV- Handbook of Industrial Organic Chemistry. ; .'. SJ-> • Pi-vSadtler. J. B. 

Lippincott Co. Phila. 1900. 
Flesh Foods with Methods for their Chemical, Microscopical, and Bacte- 
riological Examination. C. A. Mitchell. Griffin & Co. London. 

1900. 



268 BIBLIOGRAPHY. 

Food and the Principles of Dietetics. R. Hutchinson. Wood. New York. 

iooi. 
The Cost of Food: A Study in Dietaries. E. H. Richards. J. Wiley & 

Sons. New York. iooi. 
Select Methods in Food Analysis. H. Leffman and W. Beam. P. Blakis- 

ton's Son & Co. Phila. 1905. 
Suggested Standards for Food and Drugs. C. G. Moor. Bailliere, Tindall 

& Cox. London. 1902. 
Enzymes ?,nd their Applications. J. Effront. Trans. S. C. Prescott. J. 

Wiley & Sons. New York. 1902. 
Foods: their Composition and Analysis. A. W. Blyth and M. W. Blyth, 

Griffin & Co. London. 1903. 
Food Inspection and Analysis. Albert E. Leach. Wiley & Sons. New 

York. 1904. 
Organic Analysis. Henry C. Sherman. Macmillan Co. New York. 

1905. 
Foods and their Adulteration. H. W. Wiley. P. Blackiston's Son & Co. 

Phila. 1907. 



The following bulletins of the United States Depart- 
ment of Agriculture will also be found useful for study or 
reference on the general question of food: 

Office of Experiment Stations, Bulletins. 

Ko. 9. Fermentations of Milk. 1892. 

11. Analyses of American Feeding Stuffs. 1892. 

ai. Chemistry and Economy of Food. 1895. 

No. 25. Dairy Bacteriology. 1895. 

28. (Rev. Ed.) Chemical Composition of American Food Materials 

1895. 

29. Dietary Studies at the University of Tennessee. 1896. 

31. " " " " " " Missouri. 1896. 

32. " " " Purdue University. 1896. 

34. Carbohydrates of Wheat, Maize, Flour, and Bread. 1896. 

35. Food and Nutrition Investigations in New Jersey. 1896. 

37. Dietary Studies at the Maine State College. 1897. 

38. " " — Food of the Negro in Alabama. 1897. 
40. " " in New Mexico. 1897. 

43, Composition and Digestibility of Potatoes and Eggs. 1897. 

44. Metabolism of Nitrogen and Carbon in the Human Organism. 1897. 



BIBLIOGRAPHY. 26 9 

45> A Digest of Metabolism Experiments. 1897. 
46. Dietary Studies in New York City. 1898. 

52. Nutrition Investigations in Pittsburgh, Pa. 189&. 

53. " " at the University of Tennessee. 1898. 

54. " " in New Mexico, 1898. 

55. Dietary Studies in Chicago. 1898. 

63. Experiments on the Conservation of Energy in the Human Body. 
1899. 

66. Creatin and Creatinin. 1899. 

67. Bread and Bread Making. 1899. 

69. Experiments on the Metabolism of Matter and Energy in the Human 
Body. 1899. 

71. Dietary Studies of Negroes. 1899. 

75. " " " University Boat Crews. 1900. 

84. Nutrition Investigations at the California Agr. Expt. Station. 1900. 

85. Investigations on the Digestibility and Nutritive Value of Bread. 

1900. 
89. Effect of Muscular Work on Digestion of Food and Metabolism of 

Nitrogen. 1901. 
91. Nutrition Investigations at the University of Illinois, etc. 1901. 
98. Effect of Severe and Prolonged Muscular Work on Food Consump- 
tion, Digestibility, and Metabolism. 1901. 

101. Studies on Bread and Bread Making. 1901. 

102. Losses in Cooking Meat. 1901. 

107. Nutrition Investigations among Fruitarians and Chinese. 1901. 
109. Metabolism of Matter and Energy in the Human Body. 1902. 

116. Dietary Studies in New York City. 1902. 

117. Effect of Muscular Work upon Digestibility of Food and Metab- 

olism of Nitrogen. 1902. 
121. Metabolism of Nitrogen, Sulphur, and Phosphorus in the Human 

Organism. 1902. 
126. Digestibility and Nutritive Value of Bread. 1903. 
129. Dietary Studies: Boston and other Places. 1903. 
132. Further Investigations among Fruitarians. 1903. 

Division of Chemistry, Bulletins. 

No. 13. Foods and Food Adulteration — (Ten Parts). 1887-1902. 

45. Analyses of Cereals. 1895. 

46. Official Methods of Analysis. 1895. 
50. Composition of Maize. 1898. 

59. Composition of American Wines. 1900. 

61. Pure Food Laws of Foreign Countries. 1901. 

65. Provisional Methods for Analysis of Foods. 1902. 

66. Fruits and Fruit Products. 1902. 
69. Foods and Food Control. 1902. 

72. American Wines at Paris Exposition of 1900. 1903, 



%70 bibliography; 

. Farmers' Bulletins. ... 

. -..'i.\ . .-.'...•■=: . :■•>.;•?•! •::•.;.-: r ';-b. 

No. 23. Foods : Nutritive Value and Cost, i 894, : : 

29; -Souring of Milk. ! • tSg 5 . * • ■ ■■ ! 

34. Meats: Composition and Cooking. 1896. .;•:*' 

74. Milk as Food. 1898. .,,>. .!:i-: . ■•,-•. 

•Yi 85. FiSh: a ! S Food.' 1898.;- : ; "J : • ■:^:'i '. .; ,.:;:, .. :■;.: i ... > 
03. Sugar as Food. 1899, <k< 
1 1 2. Bread and the Principles of Bread Making; 1 stftjddji '•- : ') 

121. Beans, Peas, and other Legumes as Food. (190108 hi v » 
; 128. Eggs and their 1 Uses as Food. 1901. 

131. Household Tests for Detection of Oleomargarine and Renovated 

Butter. 1901. . i ; 

142. The Nutritive and Economic Value of Food 1961. • v 

i / ■■■•(: Bureau of Chemistry Bulletins.' : . ; 

No. 77. Olive Oil and Its Substitutes. 

84. I flue nee of Food Preservatives and Artificial Colors on Digestion and 

Health. 
100. Some Forms of Food Adulteration and Simple Methods for their Detection. 
107. Official arid' Provisional Methods of Analysis, 
j 10. Chemical Analysis and Composition of American Honeys. 
114. Meat Extracts and Similar Preparations. 

Much valuable information will also be found in the monthly bulletins and 
(reports of several of the State experiment stations and boards of health, notably 
those of Connecticut, North Dakota, Maine, Kansas, New Hampshire, Vermont, 
and Massachusetts. 



INDEX. 



PAGE 

Acceptable water 80 

Acid hydrolysis, of starch 211 

mercuric nitrate, preparation of 260 

, sulphanilic, reagent for nitrite test 257 

, sulphuric, reagent for air analysis 255 

, " , free from nitrogen 258 

Acids, determination in wine 220 

, volatile, in wine 220 

Adams' method for fat determination 175 

Adulteration, cause of . 156 

defined 156 

, extent of 160 

Air, amount required per capita 20 

currents, location of 25 

, composition of expired ip 

, ' ' inspired 10 

, dust in 18 

, effect of humidity in 14 

essential to life 3 

, occasional impurities in 16, 17 

of cities 17 

, variations in composition of 12 

, water vapor in . 14 

Albumin, determination in milk . 184 

Albuminoid ammonia, in relation to organic nitrogen 108 

in water, determination of 100 

Alcohol, determination in lemon extract 232 

, " "wine 217 

, table for determining 244 

-extract ratio 218 

Alkalinity in water 119 

Alkaline permanganate, reagent for water analysis 256 

Aluminum hydroxide . . 259 

.271 



272 INDEX. 

PAGET 

Alum in water, determination of x 3* 

Alumina, milk of, reagent 259 

Ammonia, standard solution, preparation of 257 

, presence in water *-g 

, in water, determination of ICK > 

Analyses, interpretation of g 2 

Aqueous vapor, tension of 236 

Ash, determination in cereals 206 

, in wine 218 

, of milk 1 73 



Babcock method for fat determination 1 76- 

Barium hydroxide, reagent for air analysis 255 

Beer, analysis of , 224 

Benzoic acid, detection of 223 

Bibliography 263 

Biological examination of water 135 

Boric acid, detection in milk 188 

Breakfast foods 161 

Brook water 86 

Butter, analysis of 193 

, complete analysis of 204. 

, composition of 191 



Calcium chloride, standard solution of 259 

Calorie, definition of 148 

Cane-sugar, detection in milk 185 

Caramel, detection in vanilla 230 

Carbohydrates, function of 146 

, separation in cereals 209 

Carbon dioxide, amount expired 15 

, determination of, in air 27 

, "popular tests" for 40 

as a disturbing factor 12 

, properties of 21 

table of weight of cubic centimeter of 237 

in water, determination of 1 29 

, a test of ventilation 23 

Carbonaceous matter in water, determination of 112 

Carbonic acid in water, determination of free 129 

Carbon monoxide, detection of, in air 49 

, estimation of, in air 50 

, effect on blood 16 

Change on ignition 117 



INDEX. 



27^ 



PAGE 

Chlorine in ground water go- 
water, determination 113 

' ' , source of 71 

Casein, determination of j#4 

Citral, determination of 233 

Clark's method for hardness 117 

Classification of waters &$ 

Cocoanut oil, detection in butter 195 

Cohen method for carbon dioxide 48. 

Collection of water samples 94 

Color of water, determination of 130 

standards for water 1 3°~ 1 3$- 

Colors, detection of 221 

, " in milk 186- 

in food 163 

Condensed milk, analysis of 189 

, composition of 189. 

Cooking, changes caused by 148 

Coumarin, determination of ,.. 227 

, Leach's test for 228. 

Cream, determination of 171 

" Crowd poison " 18-24 

Crude fibre, determination of 214 

Cycle of nitrogen 65 

Dextrin, estimation in cereals 21a 

Diastase, estimation of starch by 212 

Dietaries 152 

Dissolved oxygen, reagents for, preparation of 260 

in water, determination of 1 23 

Distilled water 73. 

Dust and soot 54, 55, 56 

, estimation of, in air 54 



Ether, anhydrous, preparation of 261 

extract of cereals 206 

Extract in beer-wort, table for 249 

... , determination in beer 224 

, "wine 217 

in wine, table of 247 

Fat, determination of, in milk 175 

Fats, value of 145 

Fatty acids, determination of, in butter 196 



274 /INDEX. 



PAGE 



Fehling's solution, preparation of . , * 261 

Filters r , r 87 

Fitz and Wolpert 43 

method for. carbon dioxide 45 

shaker 45~47 

Fluorides, detection of ,. -. 226 

Food, composition of . . . .143 

, definition and uses 143 

, principles — ........... 143 

, materials, table of composition of . . . . . 150 

, predigested .. .... 162 

.Formaldehyde, detection in milk 187 



Glass pipe . 94 

Glycerine, determination in wine 219 

Gottlieb method for fat estimation 178 

Ground water, history of 62 

Gunning method for nitrogen 209 

Hanus' iodine solution, preparation of 260 

Hardness in water, determination of 117 

, table of 242 

Heat of combustion, values for 148 

Humidity in air, effect of 14 

Ice, rules for use of 72 

Interpretation of water analysis 82 

Iodine value, determination of 197 

Iron in water, determination of — 127 

, standard solution of 259 

Kjeldahl method for nitrogen 206 

Lactose, estimation of 181 

Lake water -. . ■ 84 

Lead acetate, basic, preparation of 261 

in water, determination of 139 

, standard solution of 260 

Lemon extract 23 1 

oil, determination of 23 2 

Lime water, reagent for air analysis 255 

.Loss on ignition in water, determination of 115 



INDEX. 275 

;. >T PAGE 

Malt extract, preparation of ... ..... ,..„. 213 

Melting point of butter 2or 

Meteoric water . . 59 

Micro-organisms, estimation of in air 51 

, role of, in water 65 

Milk, acidity of . . 172 

, adulterations of 184 

, composition of ■, .■ 168 

, fermentations of 169 

, reaction of 172 

, relation of constituents . 179 

, United States standard 169 

sugar, estimation of 181 

Mineral salts, value in food 147 

substances in water 91 

Misbranding, defined 157 

Mountain " sickness " 13 

Nutritive ratio 149 

Nitrates in ground water ^. 91 

in water, determination of no 

Nitrate standard solution, preparation of 258 

Nitrogen, cycle of 65 

, determination of, by Kjeldahl method 106 

essential to living matter 75 

, total organic, determination of, in water 106 

Nitrogenous substances, function of 144 

Nitrites in water, determination of 108 

estimation of , in air 51 

Nitrite standard solution, preparation of 257 

Naphthylamine acetate reagent for nitrite test 257 

Nessler's reagent, preparation of 256 

Odor of water, detection of 133 

, analytical value of 88 

Oleomargarine 192 

Opacity of milk 171 

Organic matter in the air 52 

nitrogen in water, determination of . 106 

*' Oxygen consumed," determination of 112 

Oxygen dissolved in water, determination of 123-129 

table for 242 

Pentosans, determination of 213 

Pettenkofer method for carbon dioxide 28 



276 INDEX. 

PAGK 

Petterson and Palmquist apparatus 40 

Phosphates in water, determination of 1 20 

Purified vs. clarified water 69 

" Popular tests " for carbon dioxide 70 

Potassium chromate, reagent, preparation of 259 

ferrocyanide 61 

hydroxide 258 

iodide reagent, 261 

sulphide reagent 262 

sulphocyanide reagent 259 

Pressure, influence on respiratory exchange 13 

Preservatives in food 163 

Proteids of milk, determination of 183 

, Kjeldahl method for 206 

Residue on evaporation, determination of 115 

Reducing sugar, determination in beer 225 

Reducing sugar, Munson and Walker's table for 248 

Refractive index of butter 201 

Refractometer, Abbe 202 

Reichert-Meissl number 194 

Renovated butter 192 

, detection of 200 

Resins, detection in vanilla 229 

Respiratory exchange 15 

quotient 14 

River water 85 

" Safe " water 75-79 

Salicylic acid, detection of 223 

Salt, determination in butter 204 

Samples, collection of water 96 

Sanitary chemistry, scope of 1 

science, importance of 2 

Sediment of water, estimation of 136 

" Sewer-air " 1 7-24 

Shallow wells 90 

Silver nitrate, chlorine reagent 259 

Soap, standard solution of 259 

Sodium carbonate, detection in milk 188 

chloride, standard solution 258 

Solids of milk 173 

Soot, estimation of, in air 54 

Specific gravity of butter 201 

milk 170 



INDEX. 



277 



PAGB 



Specific gravity of milk, table for 243 

wine 216 

Spoon test 199 

Springs 88 

Starch, detection in milk 186 

, determination of 211 

Steam vacuum 50, 51 

Storage of water 71, 87 

Sugars, determination in cereals 210 

Sulphites, detection of 225 

Surface water 85, 89 

, character of 72 

Turbidity of water, estimation of 136 

Turmeric, detection of 233 

Vanilla extract 226 

Vanillin, determination of 227 

Ventilation, apparatus to illustrate r 24 

, natural vs. artificial 23 

a necessity 19 

, principle of 22 

, requirements of 26 

, to test efficiency of 24 

Vital capacity 10 

Walker method for carbon dioxide 34 

Water, acceptable 82 

Water analysis, blank form for 141 

, points to determine in 80 

, statement of results 140 

, value of 94 

Water, classification of 85 

, circulation of 61 

, determination in butter 204 

, illustration of contamination of 62 

, its relation to health 66 

, legal restrictions upon use of 57 

, need of 6 

, passage through the ground 64 

, preliminary inspection of source of 80 

, presence of organisms in 66 

, solvent power of 65 

, storage of 71 

j the ideal drinking-water 59 



78 INDEX. 



PAGE- 

Water-rvapor in air ...... .. . . . ■ 16 

Water siphon — 48, 49 

<. j daily quantity needed ....... 6 

Water-pipes ... 94 

Waters, table of average composition of .... 238 

normal . 239 

,. polluted, table of . . 240, 241 

Water free from ammonia, preparation of 255: 

, determination in cereals • 2p|i 

"- ."milk. ' :c/,.j&f 

Well-water . — .-,=....:.■ , &w. arw&bcjd 

Wine, analysis of ................. .. . r 216 

, composition of 215 

Wolpert shaker ....... .----. • - - - uftrv? 47' 

Wooden pipe n?sf*~ 94-' 



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